Abstract: In order to slove the problems that working resistance overran and supports were serious damaged,a study of the support strength of fully mechanized caving face had ben done using the simulation software FLAC^3D to establish Numerical model.According to Interactive principle between surrounding rocks and support,roof displacements of different supporting strength in stope face was simulated and the relationship between the supporting strength and subsidence of top coal in roof-control area was analyzed.The result showed that supporting strength now using was relatively low and the reasonable support strength was 0.91 Mpa.Based on the simulation results,hydraulic supports were replaced according to the principle of the three machines fully mechanized equipment choice.After that,hydraulic supports kept in good condition and resistance met production requirements.This indicates that the supporting strength determined by FLAC^3D simulation met roof activity requirements of fully mechanized caving face in this coal seam.