In the open source community, the code level of different developers varies, and code reviews are required to check the quality of the submitted code. Decision makers are the key persons in the code review, auditing the submitted code and finding software defects. Code reviews affect the quality of open source software. Therefore, it is necessary to establish code review process measurement system, understand the code review situation, and promote the quality of open source software projects. Existing software process measurement methods mainly consider code submission and review comments, but lack of consideration for decision making activities, and it is difficult to fully measure the review behavior. This study considers decision-maker factor, and proposes an open source community’s review process measurement system, including evaluation activity indicators and personnel distribution indicators. Review activity indicators include numbers of review, length of review information, number of lines that code changes, and review time. The personnel distribution indicators mainly consider the proportion and number of modifiers, commenters, and decision makers. Then, this study collects data from three popular open source projects and analyzes the relationship between evaluation process metrics and the number of software defects. Through empirical research and analysis, it is found that the number of decision-makers, the proportion of decision-makers with few changes, few comments, and few decision-makers are moderately positively correlated with the number of software defects. At the same time, compared with the measurement system without the decision maker, it is found that the measurement system with the decision maker has a higher correlation with software defects. The results of the empirical study verify the effectiveness of review process measurement system, and illustrate the necessity of adding relevant indicators for decision makers.