The instability of loess slope is one of the engineering problems that urgently need to be solved in geotechnical engineering. Firstly, the loess slope in Northern Shaanxi is selected as the research object. Four field simulated rainfall experiments under the condition of rain intensity are carried out. The boundary conditions of the slope are improved by digging the isolation groove on both sides of the slope. The changes of the depth of the water immersion and the soil moisture content of the soil under different rainfall intensity conditions are measured. Then, we analyze the rainfall infiltration process and slope stress variation characteristics under different rain intensity conditions, and compare the differences between different infiltration laws under different rain intensity conditions. The test results show that the rule is as follows. The deepest infiltration is at slope toe. The second is at slope crest. The last is at slope middle surface. The infiltration rate is the fastest at slope crest, followed by the slope toe, and the last at the middle slope. The rainfall infiltration capacity gradually weakens as the depth increases. The volumetric water content and earth pressure change amplitude of the measuring point at the same buried depth become larger with the increase of rain intensity. The time is shortened for the abrupt change of water content and soil pressure. The effect of the scour is more obvious. Finally, the seepage analysis based on Geo-studio software verifies the correctness of the field test results and clarifies the influence of rain intensity on rainfall infiltration of loess slope.