Aiming at the problem of dynamic pressure induced by overburden fracture in the square area of the first face in western mining area, based on theoretical analysis, we studied the risk of dynamic pressure in the square area of faces of different widths by analyzing the probability of overburden fracture and the dynamic pressure. The results show that, the number of key strata differs in different buried mines, breaking interval of each key strata distributes randomly and uniformly. Each key layer has the possibility of breaking in the square area. When the width the first mining face are 100 m, 200 m and 300 m, the probabilities of strata breaking in the square area are 18.2%, 9.1% and 6.1%. With the expectation loss method, it is found that the risk of dynamic pressure in the square increases with face width increases. To strengthen the protections of dynamic pressure in the square area is needed, and the measures of adjusting face, strengthening support, and directional hydraulic crack in high strata are given.