Abstract: Drilling and blasting is still the most widely used method for rock breaking in mining engineering, underground tra c engineering, hydro-power engineering, etc. The in-situ stress field and structural plane such as joint and fault all have great impacts on blasting load propagation and rock fragmentation. In the present model, a mechanical model for rock blasting is established with consideration of in-situ stress field, in which rock blasting duration is considered as two consecutive stages, i.e. firstly the dynamic stage caused by the stress wave and then the static stage caused by explosion gas pressure. The seepage equation is used to describe the explosion gas propagation in cracks and the mechanical effect of quasi-static pressure of explosion gas near the crack tip is reflected based on seepage-mechanical coupling theory. Blasting stress wave mainly initiates crush zone and radial microcrack zone, while explosion gas pressure can then squeeze into the cracks and lead to crack extension. The proposed model can reproduce the whole process of initiation and extension of crush zone and radial cracks. Numerical simulations on two-hole blasting of rock under different joint angles and in-situ stress conditions are carried out and it indicates that in-situ stress conditions would go against the initiation and propagation of blasting induced crack, while the existing joint would play a positive role on crack extension as well as a guide role on crack propagation along joint orientation.