Using silica fume and ground granulated blast furnace slag ( GGBS) as auxiliary cementitious materials and polyhydroxylic acid high-performance water reducer, the effects of silica fume and GGBS on the compressive strength of high volume fly ash mortar were studied. The pore structure, microstructure, and phase composition of prepared specimens were analyzed by mercury intrusion test (MIP), scanning electron microscope (SEM) and X-ray diffraction (XRD), and the mechanism of the effect of silica fume and GGBS on the strength of high volume fly ash mortar was obtained. The results show that with the increase of silica fume content, the compressive strength of high volume fly ash mortar mixed with silica fume increases first and then decreases. The law of GGBS mixing is similar to that of silica fume. Whether it is mixed alone or mixed, silica fume and GGBS are mixed together, the strength of mortar is improved compared with other age groups, and they show good synergy. Both silica fume and GGBS can improve the strength of high volume fly ash mortar. The total porosity and proportion of macropores of mortar specimens are negatively correlated with compressive strength. The higher the strength of mortar specimens is, the denser the microstructure is. But compared with the total porosity, the proportion of pores and macropores shows a better correlation with compressive strength. When the mass fraction of silica fume and GGBS is 8% and 6% respectively, the strength of mortar at 28 d is the highest, which is 88. 05 MPa.