Abstract: A scientific cognation and understanding of the pressure weighing in a square meter phenomenon could effectively prevent and contral the roof dynamic disaster. Based on the solutions to the mechanics mechanism formed by the breaking structure of the hard rock strata, the paper discussed the main influence factors 0 f the roof breaking form, different roof initial breaking form and the conversion law and provided the realization condition of the roof square weighing. With the statistical analysis on the breaking form of the hard rock strata in the national partial coal mines, the results showed that the condition to realize the roof square weighing was har sh and the breaking form in the statistic results was in the percentage of 4. 54%. Therefore, in the dynamic disaster prevention and control engineering, a square weighi ng phenomenon should not over stressed not based on the condition, the different type roof weighing should be effectively monitored and measured and the roof breaki ng and weighing prediction method should be scientifically discovered.