Abstract: The importance of the vacuum pressure in the VARI process system to the quality of molding was analyzed. In this paper, experiments were designed and conducted to investigate the effect of position and degree of vacuum leakage to the quality of the composite. Leakage sites were pre-installed before the inlet valve, after the outlet valve, and between the inlet valve and the outlet valve of the VARI process separately, and the leakage severity was controlled by the size of the leakage site. The test articles produced with different leakage sites and different leakage severities were examined on appearance evaluation, thickness test and ultrasonic defect detection. And the open hole compression performance of different test articles were tested. Provided that slight vacuum leakage is present in the system, the corresponding effect on the final quality of the composite article prepared by VARI process should be judged according to the leakage sites. Provided that serious vacuum leakage is present in the system, the final quality of the composite article prepared by VARI process will be seriously affect regardless of the leakage sites. The open hole compression (OHC) strength of VARI molded composite laminate plate and the porosity of the article have an inverse relationship.