Abstract: Based on the theory of fluid flow and solid elastic deformation as well as the criterion of the propagation path when hydraulic fracture meets natural fracture, a model for the propagation of hydraulic fracture through layer is established in order to accurately judge the propagation path when hydraulic fracture meets interlayer interface in coal measure composite reservoir fracturing process. The model mainly considers the effect of injection rate and viscosity of fracturing fluid on the propagation of hydraulic fracture through the layer, and gives the critical fracture pressure of the propagation of hydraulic fracture through the layer and along the interface. The propagation behavior of the fracture is judged by comparing the wellbore water pressure with the two critical fracture pressures. The accuracy of the model is verified by comparing the prediction results of the model, the fracturing test data and the on-site fracturing results. The accuracy of the model is verified by comparing the prediction results of the model, the fracturing test data and the on-site fracturing results. The results show that injection rate and fracturing fluid viscosity can directly affect the water pressure in the wellbore, and then change the fracture propagation path. The greater the viscosity between injection rate and fracturing fluid, the more beneficial it is for hydraulic fracture penetration, and the greater the influence of injection rate is. In the process of in-situ fracturing, the purpose of penetrating fracturing can be achieved mainly by increasing the injection rate of fracturing fluid.