Abstract: This paper studies the stress distribution in horizontal wellbore systematically, utilizes the numerical simulation software FLAC3D to build 3D model; simulates the effect of tectonic stress differences of different source rocks and the depth of horizontal hole on stress distribution characteristics near horizontal wellbore by fully considering the formation tectonic stress and impact of reservoir rock mechanics; provides theoretic basis for calculating the horizontal well fracturing pressure, the fracture initiation azimuth and perforation engineering optimization.