Abstract: For the sudden roof caving instability problem of 311102 working face of soft thick coal seam roof in large section coal roadway, combined with field investigation and theoretical analysis, the instability mechanism of roof was analyzed. The roadway deformation mechanical mechanism was I_CII_BDIII_BC. One of the major causes of roadway instability was the soft and thick roof and high stress of surrounding rock. Another main cause was that the large span roadway made central roof bear larger tensile stress. For the deformation mechanical mechanism of the roadway, we use the anchor mesh cable belt to control roadway surrounding rock. Based on the numerical simulation, the good effect of anchor mesh cable belt supporting method in controlling the surrounding rock deformation and the plastic zone extension was proved. Reinforcing supporting measures of 311102 working face auxiliary transport gateway was proposed. The good supporting effect was obtained and the safety in production was kept.