Compared with most solid materials such as metal, crystal and ceramics, silica glass has lower mechanical energy loss and it is the preferred material for many precision measuring devices. In this paper, the mechanical energy loss of four types of silica glass (Ⅰ, Ⅱ, Ⅲ and Ⅳ) were tested and compared. The influence factors and mechanism of intrinsic loss of silica glass were analyzed from material chemical composition and structural defects. The results show that the intrinsic losses of type Ⅰ and type Ⅱ silica glass are significantly higher than that of type Ⅲ and type Ⅳ silica glass. The main reasons are the high content of metal impurities and low bubble grade. Hydroxyl content is not the main factor that has significant impact on the intrinsic loss of silica glass. Surface loss is one of the main sources of mechanical energy loss of silica glass devices, and wet etching is an effective method to eliminate the surface loss.