Considering the difference of mechanical properties between rock and soil mass, the mechanical analytical model of tunnel excavation in geotechnical composite stratum is established using the complex variable function combined with stochastic medium theory. Then the theoretical calculation results are compared with numerical simulation and field measurement results. The results show that the analytical solution and numerical solution are in good agreement with the measured values, and the settlement trough width of numerical solution and theoretical solution are consistent, which indicates that the theoretical calculation method has high reliability. Then the effects of different vertical loads acting on rock-soil interface, the ratio of buried depth to radius of rock tunnel and Poisson’s ratio of rock mass on surface deformation and stress around tunnel are discussed. The results show that with the increase of the vertical load of the rock-soil interface, the surface settlement also increases, and the circumferential compressive stress around the tunnel increases significantly near the arch waist, while the circumferential tensile stress of the vault changes relatively slowly. With the decrease of the depth-diameter ratio h/r, the surface subsidence also increases. When h/r≥3, the increase of the depth-diameter ratio has a relatively small impact on the circumferential stress around the cave. The greater the Poisson’s ratio of the rock mass, the smaller the surface settlement, and the more uniform the circumferential stress distribution around the cave, and vice versa.