Abstract: The deformation and failure of the loess slopes is more likely to occur during the rainfall, and have caused significant losses. In order to reduce the impact of loess landslides induced by rainfall, it is of practical significance to carry out the field experimental study on rainfall-induced landslides. The natural loess slope chosen in this article is located at Jingyang. Based on the rainfall simulation system designed by us, we designed and conducted three groups of field tests of loess slope with different rainfall intensities, aiming at investigating osmotic law and deformation and failure mode of the natural loess slopes under the different rain fall intensity. By analyzing the changes of readout of soil moisture sensors, earth pressure cells and tensiometers buried in the slope and experimental phenomenon, we obtained the deformation and failure law of field test of large loess slope under the artificial rainfall condition, and the law of water infiltration, and meanwhile we summarized deformation and failure mode of this kind of slopes. The experimental results show that, the rainfall infiltration on the loess slope present certain rules during the tests, which are:the infiltration depth and seepage rate of slope shoulder are the largest under rainfall condition, followed by slope toe, and that of middle slope location are the smallest. Moreover, the greater the rainfall intensity is, the lager the infiltration rate of loess is, the longer the infiltration time is, and the bigger the increasing range of the soil pressure and volume moisture at the same position and the decrease magnitude of the matrix suction are. Under the condition of rainfall, the deformation and failure mode of natural loess slope is:①formation and extension of erosion at the shoulder of slope; ②emergence and development of fractures in the slope surface; ③occurrence and growth of fissures at the shoulder of slope; ④local caving of the slope. If it continues to rain, some cracks at the shoulder of slope will penetrate each other gradually, the sliding surface can be subsequently formed, and landslide can occur eventually.