Abstract: Fracture mechanics is usually applied to the research of hydraulic fracture.However,since both elastic strain and injure strain often occurs in the rock of hydraulic fracture,the proposes that fracture mechanics and damage mechanics need be integrated to study the rock rupture process.While using fracture mechanics to analyze cracks,this paper also presents three fracture models and introduces the damage mechanics to analyze the extension mechanism of hydraulic fracture in trachite and the distribution of stress,strain,and damage field on the borehole face.The rock mechanics parameters related to the compressive and tensile strength,Poisson’s ratio,and elastic modulus are acquired from the stress test of the interrelated core in Xiaolongwan area in Liaohe Oilfield.The equations of stress strain of the damage for trachite and the distribution of stress,strain,and damage field on the borehole face are deduced based on using damage mechanics.The research results have guiding significance on the development of the trachite reservoirs.