Abstract: Field plots were established in red soil sloping farmland with four biochar application rates(0%, 1%, 3% and 5%). Soil infiltration characteristic parameters were measured at three crop growth stages(early, middle and maturity) using a simple double-ring infiltrometer. The variations and differences in soil infiltration parameters under different biochar application rates and growth stages were analyzed, and the infiltration process was simulated using the Philip, Kostiakov and Horton models. The results showed that:(1) With the increase of biochar application rate, soil porosity and soil water content increased, whereas soil bulk density decreased. Correlation heatmap analysis indicated that soil bulk density was significantly positively correlated with initial infiltration rate and cumulative infiltration, while soil porosity was significantly negatively correlated with cumulative infiltration.(2) The soil infiltration characteristic parameters(average infiltration rate, steady infiltration rate and saturated hydraulic conductivity) of plots with different biochar application rates generally exhibited a “U-shaped” pattern, increasing at the early growth stage, decreasing at the middle stage, and rising again at the maturity stage. Considering all three growth stages, the overall order of soil infiltration rates in red soil sloping farmland under different biochar application rates was 0% > 1% > 3% > 5%.(3) Among the three models, the Kostiakov and Horton models generally achieved higher fitting accuracy in most treatments, whereas the Philip model showed relatively larger fitting errors under the 5% biochar application rate. Soil bulk density and porosity are the key factors affecting the soil infiltration process under different biochar application levels. Biochar application significantly suppresses soil water infiltration, and this inhibitory effect becomes more pronounced with the increase of biochar application rates and the crop growth progresses. All three infiltration models can satisfactorily simulate the soil infiltration process, and their simulation accuracy is mainly affected by the combined influence of biochar application rate and crop growth stage.