In this paper, using laboratory experiments and theoretical analysis, gas desorption properties are studied at different adsorption balance pressures and sizes for different types of tectonically soft coals. Values of desorption indexes K_1 and⊿ h_2 are measured for different types of tectonically coals ,and the function of K_1 and⊿ h_2 are induced and validated. Based on desorption laws, the differences between K_1 and⊿ h_2 in gas desorption forecast are showed. By analysis on desorption results of differe...