Abstract: Erosion-wear performance in gas-solid of cement mortar subjected to freeze-thaw cycles in composite salts solution was studied by using sediment-air injection method. Based on the SEM, the laser scanning confocal microscopy (LSCM) and XRD, surface morphologies of specimen after erosion and the chemical composition of specimen surface before and after freeze-thaw in salts solution were measured to explore the erosion damage mechanism. Results show that in the same erosion conditions, erosion rate increases as the impact angle increase, and the growth tendency in the high impact angle is relatively slower; The erosion rate firstly decreases and then increases with the increasing freeze-thaw cycles in composite salts solution, and the erosion rate reaches minimum at freeze-thaw of 10 times; Under the same condition, the erosion rate in 8% concentration is a little higher than that in 10% concentration. In the erosion damage process, normal components of kinetic energy play a decisive role, which is characterized by the emerging of erosion pits and micro-damage zones. The effect of freeze-thaw in composite salts solution on erosion-wear performance is mainly reflected in two aspects as follows. Physical aspects:the effect of supersaturated solution crystallization in the cooling process, ice expansion pressure and osmotic pressure on internal pores; Chemical aspects:ettringite and gypsum crystal generated through the chemical reaction between anion and cement-based materials filling in inside of cement mortar, improving its compactness. However, the increasing pressure can promote crack formation in the later stage, which has a negative effect on the erosion-wear resistance of cement mortar.