The external and internal hydro-proof test investigation of the cylinder structures are developed in the present paper. The needling C/C composite cylinder sample preparation and the fixture are designed according to the testing condition. The stress distribution information of the structures is obtained during the test process. The 3D hydro-proof FEM simulation model is established to compare with the experiment results. The simulation results are in good agreement with the test results,which indicates the validity and accuracy of the FEM simulation model. The test and simulation conclusions can provide some important guidance for the nozzle carbon/carbon composite with cone structure design, material constitutive model parameter modification and structure safety tolerance prediction.