Abstract: Based on the reason analysis and prevention countermeasures of critical top-caving accident at 8107 fully mechanized caving face in Tongxin Coal Mine, common cause failure reliability calculation analysis method of hydraulic support system was proposed. Combined with the definition of hydraulic component condition failure probability, common cause failure discrete formula was deduced by using statistical methods. Formula derivation and application practice showed that hydraulic system failure probability depended on the contribution of roof loads and hydraulic component performance. Since their discrete degrees were different, during the calculation analysis, it was necessary to consider the correlation and respond to discriminate between them. Hydraulic system reliability of single-frame support column was 99.6% in 8107 fully mechanized caving face, but the overall reliability was lower for the series connection system of No.110 fully mechanized hydraulic supports.