The acquisition and accuracy of information of rock mass discontinuities structural plane are the key to the safe tunnel excavation. A new 3D reconstruction method for rock mass structure based on ASIFT algorithm and RANSAC algorithm is proposed so as to improve the efficiency of 3D reconstruction algorithm. The ordinary digital camera is used to gain a series of digital images of real rock mass structure quickly. And then, according to the characteristics, i. e. large variation of rock mass image scale and angle of inclination, and poverty of texture of rock mass, the ASIFT matching algorithm and RANSAC mismatching point elimination algorithm are adopted to guarantee the efficiency and reliability of the sparse matching between stereo images. Finally, the bundle adjustment method in conjunction with adjustment method is used to solve the relative position and attitude between image sequences. Meanwhile, the methods of epipolar line geometric constraint, localfull matching and least square matching are comprehensively adopted to achieve the intensive matching of rock mass images; and then 3D information of rock mass structure is finally extracted. The engineering practice shows that the noncontact measurement of rock mass structural planes can be completed conveniently by the abovementioned method; meanwhile, the efficiency can be improved and the risk of survey crew exposing under rock mass can be avoided.