As the natural barrier of the high-level radioactive waste(HLW) disposal project

the host rock is essential to ensure the stability and safety of the project in long-term. With the purpose to establish an effective method for evaluating the rock quality for site characterisation

the relation between the average structure spacing D

which is used as a quantitative index to describe the fracture distribution of rock mass

and the scores of relative metabolic rate(RMR) system is set up. It is shown that the point set

which is composed of the values of RMR and D

has a fan-shaped positive correlation. The value of D increases with the score of RMR. Moreover

the index of structure spacing D in lower order area shows a better corresponding relation with its rock mass quality than in higher order area. The method is used in the evaluation of rock mass quality around the borehole BS16 in Beishan area; and a good accordance between the distribution of D and RMR is obtained. The results suggest that it can be used as an effective and alternative approach of rock quality evaluation in the site characterization of HLW disposal project.