To simulate the influence of non-continuous rainfall on the friction of pile foundation in Lanzhou collapsible loess, field test was carried out via natural infiltration method. The project measures the pile side friction by embedding the steel bar and the immersion depth by water probe. The results show that the maximum water immersion is about 10 meters, and the increase of water content below this depth is marginal. During the test, the negative friction resistance is taking effect, and its peak increases when the load increases. At the loading stage, the length of the negative friction resistance is about 0.24 times the pile length, subjected to certain fluctuation. During the unloading process, there is still negative friction resistance, and the interval length fluctuates within the range of 0.28~0.45 times the pile length. The results show that the initial rainfall has a significant influence on the pile foundation, and the effect of continuous intermittent rainfall is marginal. The actual negative friction resistance is much smaller than the threshold. Consequently for pile design, it is necessary to fully consider the impact of the initial rainfall.The pice length should also be adjusted based on the negative friction resistance.