The compressive behavior of one-third composite cylindrical shell with opening reinforcement was studied under a compress load. The reinforced specimen was tested and failed in buckling at 65.922 kN near the open hole. A finite element model was established in ABAQUS to investigate the buckling behavior of the composite cylindrical shell. The computational results and experimental results of buckling failure mode and buckling load were compared to verify the validity of the finite element model. The results show that as opening area increases, the buckling load of the shell without reinforcement does not decrease progressively. However, in a certain range of opening area, the structure gets maximum and minimum buckling load values. While in the case of reinforcement, with the opening area being constant, the buckling load is in direct proportion with opening height, and is in inverse proportion with opening width. To considering design and workmanship, opening height should be increased.