On the basis of statistics of joints of the one-dimensional space, the method of scan line to density of joint rock mass is sensitive to the line direction and could not entirely reflect the joint developmental condition on the three  dimensional space. Usually, this approach could not ensure enough accuracy. While, the volumetric joint count J^_v which is based on the three-dimensional space of a rock mass, could reflect the joint density well. Nowadays, in the main surrounding rock classification methods at home and abroad, their evaluation indexes have a significant connection with the volumetric joint count J^_v. So it is very important to acquire the accurately volumetric joint count J^_v value. This paper introduces the calculation methods of volumetric joint count for different kinds of rock masses and its application in RMR, Q, GSI and BQ surrounding rock classification methods, and applies these methods in connection with the practical engineering.