In order to study the feasibility of the compound mineral additives composed of phosphorus slag powder and limestone powder(PL) for substituting fly ash(FA), basic characteristics of phosphorus slag powder(P), limestone powder(L) and FA were tested. Additionally, the micro structures of their cement paste were analyzed comparatively, and the performance of mechanical, durability, deformation of dam concrete with different mineral additives were tested. According to the comparison of characteristics of PL concrete and FA concrete, it is concluded that the performance of PL concrete is better than that of FA concrete on micro and macro scales, especially on the long-term compressive strength, and ultimate tensile strain scale. Besides, the PL mineral additive has lower cost as well as higher technical and social benefits. Thus, in Southwest China, where it is lacking high-quality FA, the substitution of PL additive for FA as mineral additive used in dam concrete is feasible alternative.