In order to study the optimal mix ratio of different strength grades of slag granite concrete, the metamorphic granite slag produced during the tunnel excavation of WYTJ-07 section of Wuyue high-speed project was selected to make machine-made gravel and machine-made sand. Taking the tunnel of the WYTJ - 07 section of the Wuyue Expressway as an example, the metamorphic granite slag produced in the excavation process was processed into machine-made gravel and machine-made sand. By changing the water-binder ratio and water reducing agent of granite concrete, the mixture ratio of slag granite concrete was optimized through two-factor and three-level comprehensive experiment. The results show that the slag of metamorphic granite of Wuyue tunnel can be used for concrete composition. The optimal water-binder ratios of the C15, C20, C25, C30, C40 and C50 slag granite concrete are 0.54, 0.50, 0.47, 0.43, 0.39 and 0.33, respectively, and the dosage of water reducing agent should higher than 1.0%.