Aimed at the shortcoming of macroscopic continuum theory in investigating hydraulic fracturing by presetting crack interface element, the particle flow method of micro-mechanical discrete element theory was introduced to simulate mechanical behavior of hydraulic fracturing for low permeability reservoir. The reservoir was simulated as round particle, while the fluid movement of the fracturing fluid was described by Navier-Stokes equation, and particle flow numerical model of hydraulic fracturing for low permeability reservoir was established considering fluid-solid coupling. Fracturing criteria for contact-bond model were analyzed, and PFC-CFD fluid-solid coupling solution for hydraulic fracturing in low permeability reservoir was discussed based on N-S equation, and the effects of different parameters on the fracturing behavior were discovered. The results showed that the fracture initiation pressure is proportional to the minimum horizontal stress, particle normal contact stiffness, particle normal and tangential connection strength, while the fracture length and width are inversely proportional to above parameters. In addition, the initiation pressure, fracture length and width are independent of maximal horizontal stress and tangential contact stiffness.