Abstract: The structural plane is main internal factor of determining rock slope stability.During the mine digging,the new steps slopes provide new boundary conditions to the failure of rock slope,which results in partial failure.This paper uses the Dips software to get the structural plane's dominant occurrences by field investigation,measuring and counting the occurrences of structural plane.The relationship among dominant occurrences,dip angle and dip direction of slope is used to analyze the failure type and boundary conditions of steps slope in different engineering geology zoning.Finally,the main failure type and distribution areas of rock slope in the Qinghai Songshunangou open-pit mine is obtain to provide strong support for safety in production in the open-pit mine.