Abstract: In order to solve the serious resource waste caused by sectional coal pillars, serious mine strata pressure behavior in the gateway and other problems in Tashan Mining Area, the similar simulation method was applied to study the lateral support pressure distribution features after the mining of the fully- mechanized top co al caving mining face in ultra thick seam and provide the theoretical basis to the optimized design of the coal pillar width for the gateway driving along the goaf in Tasha n Mine. The results showed that the lateral support pressure influence scope of No. 8206 Coal Mining Face in Tashan Mine was 60 ~ 70 m, the stress reduced zone wa s 11 m, the stress peak was41 MPa in the location of 30 m in front of the coal wall and the stress concentration coefficient was 3. 3. The similar simulation results and |i mit balance theoretical calculation results were the same to the site seismic monitoring and measuring results. Thus when the coal pillar width was less than 6 m and th e gateway was in the stress reduced zone, the coal pillar width obtained was 6 m.