Abstract: Soil salinization and alkalization are complex types of land degradation driven by long-term imbalance between water movement and salt accumulation. Saline–alkali soil disasters can be characterized as surface salt accumulation, vegetation degradation, hydrological imbalance, cropland productivity loss, and land use. Remote sensing has been widely used to evaluate salt-affected land and then monitor its spatial dynamics. But existing studies still focus on the retrieval of single soil parameters. This review aimed to explore the status and prospects of remote sensing in monitoring and managing saline–alkali disasters. Particularly, remote sensing information was selected to support risk identification, spatial zoning, decision making, and evaluation. Recent studies on saline–alkali land remote sensing were reviewed from the perspectives of response mechanisms, monitoring objects, diagnostic indicators, and applications. 1) The spectral, microwave, and thermal response of the salt-affected land was summarized under different climatic backgrounds, soil moisture, salt occurrence forms, vegetation cover, and surface structures, according to remote sensing signals. 2) The monitoring objects were organized into four dimensions: vegetation response, soil surface state, hydrological process, and cropland system performance. A comparison was made on the typical indicators from optical, thermal infrared, and microwave observations, including vegetation structural and physiological indicators, soil salinity and brightness indices, microwave backscattering and dielectric-related information, evapotranspiration, soil moisture, land surface temperature, and yield gap. 3) Multi-source remote sensing information was summarized to assess the surface responses, water–salt processes, and agricultural production functions. Remote sensing responses of saline–alkali disasters were strongly correlated with the soil salt, soil moisture, vegetation cover, soil texture, surface roughness, and regional environmental background. Salt crusts or spots formed on the soil surface after salt accumulation in arid and semi-arid bare or sparsely vegetated areas, leading to the high reflectance in visible and near-infrared bands. By contrast, salts were dissolved to form the moist, hidden, or root-zone forms in coastal humid regions, irrigated croplands, or areas with higher vegetation cover. Soil moisture or vegetation cover also weakens the spectral signal of surface salt. Therefore, conventional salinity or brightness indices were more suitable for exposed surface salts under bare or low cover, whereas humid, irrigated, or vegetated regions required integrating vegetation response, hydrological, and ground observations. Vegetation indicators presented the cumulative effects of saline–alkali stress on canopy structure, physiological condition, phenological rhythm, and crop growth. Soil surface indicators also provided further information on salt exposure and structural degradation, but their reliability was constrained by soil moisture and mixed pixels. Hydrological indicators (such as evapotranspiration, soil moisture, and groundwater information) were used to diagnose the driving mechanisms of salt migration and redistribution. Cropland system indicators, including crop growth anomalies, yield potential, cropping structure, and farmland abandonment, were used to further reflect the impact of saline–alkali stress on agricultural production functions. These indicators were integrated to support the differentiation areas under deep water–salt imbalance, seasonal or management-induced surface salinity, and ecological adaptation, rather than the intensive agricultural use. Remote sensing contributed to saline–alkali disaster monitoring and management by information acquisition, diagnosis, zoning, and evaluation, rather than by directly replacing engineering drainage, agronomic improvement, soil amendment, or ecological restoration. A multi-object and multi-source monitoring framework was achieved in the robustness of saline–alkali disaster diagnosis under complex environmental conditions. The practical remote sensing products were observed for decision-making. Future research should strengthen regional response mechanisms, multi-source data fusion, long-term monitoring, and the integration of remote sensing with ground observation networks, data platforms, and intelligent models. The finding can provide a strong reference to improve the continuity, precision, and accessibility of remote sensing information in monitoring and managing saline–alkali disasters.