Abstract: Small geological structures are well developed and complex in Xiahuayuan Coal mine, but medium-sized geological structures are less.These small structures are chiefly reverse faulf. wich smallthrow and asymmetrical, overturned secondary,wich are intraformational sliding structures produced by intraformational teclonism wich is derivative from the process that form the large 一scale overthrust. Research indicate that the distortion of the axis of Yudaishan syncline and its sophistjcated limbs lead to the complexity of small geological structure.To make clear the causal relationship betwees the small structure and syncline has realistic significance in guarding structural forecast and coal mining.