Slope and crop growth period are the key factors affecting the soil infiltration performance of sloping farmland, and crop growth can result in soil characteristics and root changes, which further affect the slope infiltration process. Through artificial simulated rainfall experiments, the slopes (3°, 5°, 10° and 15°) and 2 rainfall intensities (40 and 80 mm/h) of four slope cultivated land were designed, and the experiments were carried out in four growth stages of millet (early jointing period, middle jointing period, early heading period, early pustulation period) to explore the influence mechanism of slope and growth period on soil infiltration characteristics of millet slope farmland, and combined with the infiltration model (Horton, Kostiakov and Philip models) to evaluate the applicability of soil moisture infiltration process in cultivated land of millet slope. The results showed that: (1) The soil infiltration capacity decreased with the increase of slope, and compared with the slope of 3°, the stable infiltration rate, average infiltration rate and cumulative infiltration rate of the soil in farmland of 15° slope decreased by 30.76%~52.38%, 21.28%~37.50% and 22.51%~43.55%, respectively. (2) With the extension of millet growth period, soil infiltration capacity increased significantly, and compared with the early jointing stage, the stable infiltration rate, average infiltration rate and cumulative infiltration amount of soil in the early filling stage increased by 23.81%~80.00%, 20.83%~40.00% and 17.84%~54.10%, respectively, showing that the early jointing period < the middle jointing period < the early heading period < the early pustulation period. (3) By fitting the measured values of infiltration rate, the Horton model could best fit the soil infiltration process of slope farmland, and the fitting parameters of the model had physical significance. The research results can provide a theoretical basis for increasing rainfall infiltration, improving water use efficiency and reducing water and soil loss in sloping farmland.