The Yuanmou dry and hot valley of the Jinshajiang river is one of the fragmental environment areas in China,where the soil and water loss was very serious.It is difficult to interpret the peculiar soil erosion phenomenon using the traditional opinion.This study based on the observation in the environment and soil profiles which related with developed soil crevice,and using such means as chemical analysis,X-ray diffraction pattern and micromorphology.Results showed that:(1) In this area,the developed soil crevice was significant correlated with the parent material of the quaternary system old red horizon(QS) and yellow brown horizon(QY).(2) The developed soil crevice was the main reason for soil fall and gravity erosion,as the result,the soil erosion increased obviously.Finally this paper advanced a new viewpoint that soil crevice was the most important reason of the seriously soil and water loss formation.