Abstract: To gas transfinite problem of high gas top coal caving working face，according geological situation and mining technical of 10101 working face of Hongyan coal mine，based on overburden broken height of working face and high level drainage roadway position theory，the theoretical height should be arranged within 23～50.5m，and then verified by numerical simulation，the following conclusion was reached that all strata below L₄ limestone would collapsed after 9+10 coal seam was mined，collapse zone development height was about 21m，at last，high level position was layout in No.6 coal seam.