Abstract: As an important organ for crops to absorb water and nutrients, the quantification of root system is of great significance for water and fertilizer management in the field. However, compared with aboveground parts, the current studies on root system architecture are very limited, especially in saline soils. In this paper, the dynamic changes of sunflower root length density（RLD） in different salt fields（low saline S1, high saline S2） were observed by using minirhizotron based on the experimental data of saline farmland sunflower in Hetao Irrigation District of Inner Mongolia, and the three-dimensional structure of crop roots in each field was simulated by combining root system architecture model（RSA） RootBox. The results showed that RootBox could well simulate the root system of sunflower under different salinity. The simulated RLD values of minirhizotron observation site were close to the measured values, R~2 was more than 0.73 and RRMSE was less than 0.28. However, the RLD simulation accuracy of S2 field was relatively lower, and RMSE was 0.84 higher than that of S1 field. Moreover, the simulated average RLD distribution in S1 field was close to the observed minirhizotron RLD distribution, while the difference was significant in S2 field, especially in the 60-90 cm soil layer. These results indicated that the minirhizotron method and root system architecture model could provide support for quantifying the morphological structure of crop roots in saline fields, and the quantitative effect of crop roots in high saline fields was more significantly affected by soil salinity.