Abstract：Rock quality of designation (RQD) is an very important index in rock mass quality evaluation. But the reliability and engineering application of conventional RQD are limited by the direction，the number of the bore holes available in investigation and hence the notable errors. The method of obtaining RQD of rock mass by sampling window is presented in this paper. Setting scan lines in all the directions automatically by computer program，the errors can be reduced and anisotropic properties of rock mass can be synthetically reflected by this new method，and a large number of RQD can be easily obtained. The method is simple and easy to handle in engineering application.
