In order to analyze the effect of prestressed cable on the excavation stability of super-span underground engineering, taking a large span underground engineering as the example, the prestress value and space of prestressed cable were analyzed by numerical simulation. The principle of vault displacement and liner maximum principal stress under different prestress value and space of prestressed cable were obtained. The results show that with the increase of the anchor cable prestress the vault displacement and liner maximum principal stress decrease gradually, however, the maximum stress of the anchor cable shows a trend of increasing at first and then decreasing. With the increase of the space of anchor cable, the vault displacement and liner maximum principal stress increase gradually, the maximum stress of the anchor cable shows a trend of increasing at first and then decreasing. It is recommended that the prestress value of the anchor cable should be 200 tons and the space should be 5 m.