Abstract: Based on the Standard for Engineering Classification of Rock Mass, a rock mass classification method considering the engineering span effect is put forward in this paper by combining diagram-based quantized contrast with metro engineering features. The method includes adjusting the existing qualitative feature classification of surrounding rock, improving BQ indexes so that the qualitative classification is consistent with the quantitative classification, giving the sub-classification and corresponding BQ indexes for the surrounding rock of running tunnels and station tunnels based on the rock mass quality and engineering span classification and quantifying rock mass self-stability. Based on research on the physical and mechanical parameters and classification of surrounding rock for Chongqing Metro Lines 1 and 6, it is determined that on the premise of construction safety, one third of sandy surrounding rock of grade Ⅳ can be classified as that of grade Ⅲby the above classification method regarding the running tunnel, and the percentage is 80% for the station tunnel.