Ti-18Mo, Ti-18Mo-0.5Si, Ti-18Mo-1Si and Ti-18Mo-2Si alloys were prepared by high-energy ball mill and SPS. The effects of Si content on the oxidation-resistance behavior of Ti-18Mo-xSi alloys at high temperature oxidation under 700℃ and 800℃ in air were investigated by analyzing the microstructure, phase composition of sintered and oxidized alloys.The results show that the sintered alloys contain Ti(Mo) solid solution and the alloys with Si contain Mo5Si3 phase. After oxidation at 700℃ and 800℃ for 100 h, the main phases of alloys were TiO2, TiO, MoO2 and MoO3, and the oxidized alloys with Si contain SiO2 phase. The oxidation resistance of Ti-18Mo-xSi alloys at 700℃ is better than that at 800℃. Especially, Ti-18Mo-0.5Si alloy with average oxidation rate of 0.09 g·m-2·h-1and 0.10 g·m-2·h-1 at 700℃and 800℃, respectively. The oxidation resistance of Ti-18Mo-0.5Si alloy is superior to other alloys.