Ridge and furrow are the important confluence paths in soil erosion of long and gentle slope farmland. It is very important to understand the hydraulic characteristics of ridge and furrow for simulating the soil erosion process of slope farmland in typical black soil area of Northeast China. The main hydraulic parameters and variables of ridge and furrow under different ridge cultivation methods, slopes and rainfall intensities were systematically analyzed using indoor rainfall simulation method. Under different ridge planting patterns, the erosion amount were narrow ridge > wide ridge > no ridge, showing linear positive correlation with the product of slope and rainfall intensity. The variation curve of hydraulic radius with rainfall intensity and slope was logarithmic. The hydraulic radius of wide ridge was 8.4% to 11.6% higher than that of narrow ridge, with an average of 10.0%. Under the same slope and rainfall intensity, the roughness of wide ridge was higher than that of narrow ridge. Moreover, with the increase of slope, the decrease in roughness of wide ridge was weaker than that of narrow ridge. There was a significant difference between the recommended values of roughness in the existing soil erosion models and the observed values in this experiment. Therefore, it is necessary to recalibrate the roughness value for erosion process of long and gentle slope cultivated land under ridge cultivation in this area.