Abstract: The NO.3405 working face of a coal mine in Shanxi uses the fully-mechanized mining technique of mining whole height at one times, but its strata behavior is more serious. For better and safely efficient mining in the coal mining face, the characteristics of stress distribution when the working face was mined is anlyzed by FLAC^3D numerical simulation software.The research results show that where the peak of abutment pressure in advance is 5 m from coal face in NO.3405 working face, and the influence scope is 75 m from coal face, and the stress concentration coefficient is 2.3; the peak of fixed abutment pressure is 15 m from coal wall, and the influence is 45 m from coal wall, and the stress concentration coefficient is 2.0; the area of tensile stress is about 16 m in the working face.