The prevention and control of rock burst disaster has become the core problem restricting safe and efficient mining, and the problems of rock burst in hard overburden thickness change area are becoming more and more prominent. Based on the engineering background of the west third upper mining area of Hongyang No.3 Mine in the kilometer mine, the mechanism of stress anomaly disaster in the non-uniform distribution area of hard overburden thickness was systematically studied. By constructing an elastic medium model of overburden, the influence of the synergistic effect of overburden thickness and elastic modulus on vertical stress was revealed. The results showed that the stress concentration factor K could reflect the positive correlation between the thickness of overburden rock and the vertical stress. The larger the thickness of overburden rock was, the larger the stress concentration factor K was, and the more significant the stress concentration was. The thicker the thickness of the hard overburden in the roof, the higher the stress concentration of the surrounding rock of the roadway ; the measured data of vertical stress in the abnormal stress area of coal seam effectively proved that the thickness of overburden rock was an important factor affecting the vertical stress of coal seam.