Through the analysis and research on the problems of poor safety conditions and large loss of top pillars in the mining of olive-type thick ore-body under the group of mined area，it was concluded that a high-level open stoping with subsequent waste rock filling mining method which had a security barrier pillar about 25m was better to mine this thick ore-body. FLAC3D was used to simulate and analyze the structural parameters of high-level stope，and also the influence of high-level mining on the stabilities of upper mined area，security barrier pillar and upper and transportation gateway. The results show that the stope size of 40m×ore body thickness×75m and the pillar size of 10m were suitable，the stability of the big mined area was good under the protection of the security barrier pillar，and the transportation gateway of 650 needs to be changed because of the poor stability near the mine room. Through the field industrial test，the high-level mining method saved 240m of the mining preparation engineering and the mining preparation period was short. The ore was recovered by 48,000 tons without retaining the top pillar，and the stope production capacity reached 1400t/d due to synchronous blasting of large diameter deep hole and upward fan-shaped hole，the ore recovery rate and production efficiency were greatly improved which provided technical support for the mine to be put into production as soon as possible.