Abstract: Inter-well stress interference has great influence on the “well factory” development effect of shale reservoir, leading to a certain deviation of reservoir stimulation result from the design scheme. It is in urgent need to accurately analyze and clarify the fracture propagation laws under the action of inter-well stress interference. The 3D zipper fracturing induced fracture propagation model was established by means of discrete element method, the influences of horizontal principal stress difference, fracturing fluid displacement and well spacing on fracture propagation morphology were studied, and the influence degree on total fracture volume was quantitatively analyzed. It is indicated that fracture tip deflects easily when well spacing is shorter than 80 m, which means inter-well interference is obvious at smaller well spacing. The influence degree of different factors on total fracture volume is ranked as fracturing fluid displacement＞well spacing＞horizontal principal stress difference, so during field construction, fracturing fluid displacement shall be adjusted mainly to improve the fracturing effect. Horizontal principal stress difference has less influence on total fracture volume, and it mainly controls the deflection degree of fracture tip. When horizontal principal stress difference is less than 6 MPa, fractures deflect easily to form complex fracture network. Based on this, increasing fracturing fluid displacement to 0.3 m³/s and well spacing to 80 m can increase the total volume of hydraulic fractures by 47.92% from 326.36 m³ to 482.75 m³. The research result provides a reference for optimizing horizontal-well zipper fracturing process and measure and is of important significance for improving the recovery factor of shale reservoir.