Influences of single and combined addition of fly ash, ultra fine fly ash and silica fume on compressive strength, flexural strength and bonding strength of magnesia phosphate cement based rapid repair mortar were systematically studied. The hydration products and microstructure of magnesia phosphate cement mortar were analyzed by X ray diffraction(XRD) and environment scanning electron microscope(ESEM). The results show that the addition of fly ash and ultra fine fly ash results in the decrease of the compressive strength and flexural strength of magnesia phosphate cement mortar，while the addition of silica fume has little negative effect on these strengths. Incorporation of fly ash or ultra fine fly ash decreases the early bonding strength but improves the later bonding strength development rate, while bonding strength is improved effectively by the incorporation of silica fume at any age. Furthermore, mineral admixtures are involved in the hydration of magnesia phosphate cement and the generated amorphous products compensate for the strength loss, while the pozzolanic activity of mineral admixtures is the main reason for the development of bonding strength.