Abstract: Engineering Geo-mechanics of Rock Mass founded by professor Gu Dezhen last century has been one of representative scientific theories of engineering geology in China. The core of the theory is the mechanical effect of rock mass structure. The paper firstly summarizes the principles of Gu Dezhen's theory, and then introduces the exploration and progress during the past 20 years on Statistic Mechanics of Rock Mass (SMRM) which has been a development of Gu's thought. The achievements of SMRM mainly include the parameterized statistical model of rock mass structure, stress-strain relationship, strength and failure probability, and hydraulic model of rock mass. Various of mechanic and hydraulic effects and controlling regulations of rock mass structure reflected by these quantitative models have been discussed. The concept of initiative reinforcement to make use of the self-stabilization potential of rock mass and a mode of anchorage emphasizing the enhancement the slope foot have been proposed in the paper. It is pointed out that Gu's theory, Engineering Geo-mechanics of Rock Mass, has strong vitality because it revealed the basic law of the behavior of rock mass and the dominant factors of it. To promote the quantitative development of Gu's theory is a historical task of the followers.