It is hard to describe the complex fracture types. According to the rock strength damage criteria, the model of propagation when the hydraulic fractures come across the weak structural plane was studied, and laboratory experiment verified the reliability. The extending behavior of hydraulic fracture was analyzed when intersecting the weak surface using mine application. The results shows that the important factors of impacting propagation are horizontal stress differential, azimuth of weak plane and coefficient of friction. It is easy for hydraulic fractures directly cross the weak plane under higher principal stress ratio, higher azimuth and higher coefficient of friction. By contrast, it is easy to propagate along the weak plane direction under the opposite condition. This study has the important significance to understand coal-seam complex fracture forming mechanism and establish the complex fracture forming model.