The present study was conducted with the aim of influencing the impact of employee development methods on human and social capital and performance of the organization with the role of knowledge management as a mediator. The statistical population of the present study consists of employees of Babolsar Municipality, which has 700 employees. According to Morgan's table, the sample size of employees was determined as 248 and was selected based on the random sampling method. The data collection tool is a standard questionnaire that is measured with a 5-value Likert scale. The content validity of these questionnaires has been approved by experts in this field, including the supervisor, and its reliability has been determined based on the Cronbach's alpha test, using statistical software for social sciences (SPSS), and has been confirmed and approved with a high percentage (0.84). The analysis of the collected data has been examined by descriptive statistics through SPSS software and inferential statistics from the structural equation modeling method (partial least squares) and using Smart Pls software. The impact of the first, second,... and seventh hypotheses has been evaluated and confirmed with impact coefficients of 0.21, 0.24, 0.31, 0.44, 0.49, 0.51 and 0.56 at a confidence level of 95% (5% error rate). The results of the study indicate that employee development practices with a path coefficient of 0.56 have the greatest impact on knowledge management and employee development practices have the least impact on social capital with a path coefficient of 0.21.