Abstract: With intensifying climate change, greenhouse agriculture has become an important means of improving crop yield and quality, while effective temperature and humidity control is critical to crop growth. In hot and humid regions, the high energy demand of greenhouse air-conditioning systems poses major challenges, which highlights the need for renewable-energy-driven and energy-efficient climate control solutions. The solar-assisted solid desiccant hybrid air-conditioning system, which utilizes low-grade renewable energy as its energy source, is considered one of the most promising technologies for greenhouse climate control. However, in agricultural greenhouses characterized by complex thermal and moisture environments and crop-specific physiological demands, the dynamic operational characteristics of such systems and their adaptability to greenhouse air-conditioning requirements have not been fully investigated. Therefore, this study aimed to evaluate the dynamic performance and adaptability of the solar-assisted solid desiccant hybrid air-conditioning system for greenhouse climate control under hot and humid conditions. A greenhouse thermal and moisture load prediction model was developed on the TRNSYS platform, and a coupled simulation model integrating a desiccant wheel with a vapor-compression chiller was subsequently established. The period from July 1 to July 28 (4344 h–5016 h), during which Guangzhou experiences peak temperature and humidity, was selected as the representative simulation period. First, under identical operating conditions, a comparative analysis was conducted on the dynamic distributions of thermal and moisture loads in greenhouses cultivating four typical crops: tomato, cucumber, grape, and sweet pepper. The results indicate that although the overall variation trends of thermal and moisture loads are generally consistent among different crops, the ratio of latent to sensible heat varies, demonstrating that crop physiological characteristics play a decisive role in load composition. Then, the effects of key parameters—including fresh air volume, chilled-water outlet temperature, solar collector area, and electric auxiliary heating power—on system performance were systematically examined. The results show that increasing fresh air volume enhances the dehumidification capacity of the desiccant wheel, and the system performance stabilizes when the airflow reaches 1400 m³/h. Increasing the solar collector area reduces the dependence on auxiliary electric heating, thereby improving the electrical coefficient of performance (COP_el) while maintaining a stable overall system performance (COP_sys). When the chilled-water outlet temperature is maintained below 17 ℃, the guarantee rates of temperature, relative humidity, and vapor pressure deficit (VPD) all exceed 95.0%, whereas higher outlet temperatures deteriorate both temperature–humidity control performance and system efficiency. Furthermore, increasing auxiliary heating power from 4 to 12 kW slightly improves control performance but leads to increased electricity consumption, resulting in a reduction of COP_el by approximately 23.8%. Finally, the system meets the environmental control requirements of greenhouses in five representative hot and humid regions—Guangzhou, Haikou, Xiamen, Changsha, and Nanning—with temperature, relative humidity, and VPD guarantee rates all exceeding 90.0%, indicating good operational adaptability. Compared with conventional air-conditioning systems, the proposed system reduces total electricity consumption by 53.1%, improves COP_sys by 40.4%, and achieves a life-cycle operating cost saving of CNY 214,000 (equivalent to CNY 1932/m²), demonstrating energy-saving potential and economic benefits. Overall, the proposed solar-assisted solid desiccant hybrid air-conditioning system effectively addresses the high energy consumption problem in greenhouse climate control under hot and humid conditions and provides a theoretical basis for the development of sustainable and low-carbon greenhouse agriculture.