Abstract: The additive mass method (AMM) has been applied in the density tests on different materials of many earth-rockfill dams. With the development of hydropower projects in recent years, the soil-rock mixtures (S-RM) with wide gradation and high fines content have been used for dam construction. While the researches on the applicatbility of the AMM in the soil-rock mixtures are insufficient. In this study, the AMM is adopted to evaluate the compaction densities of the S-RM composing of fresh dolomite and strongly weathered diorite porphyrite in a pumped storage power station in China. The compaction densities evaluated by the AMM are compared with those measured by the pit tests. The results demonstrate that for the S-RM containing low contents of diorite porphyrite, the compaction densities can be reasonably evaluated by the AMM. For the S-RM with high contents of diorite porphyrite, the analysis of the \omega ^ - 2\text - \Delta m correlation obtained by the AMM in advance is required to conduct reasonable compaction density evaluation.