Abstract: On the basis of vertical static loading test and stress test of bored piles shaft,which built in some places in Guanzhong district along Zhengzhou-Xi'an Railyway Passenger Transportation special Line, under prewetting and afterwetting in self-weight collapse loess, the paper discusses the generating and developing procedure of negative skin friction of pile, and changing procedure of neutral point position, and the action law of lateral friction resistance. The theoretical study and engineering application on negative skin friction of pile in self-weight collapse loess can be quite reference value.