Errors and rework created in projects have been one of the most important causes of planning pressure and unsafe behaviors and then high accidents in construction workshops. The causes and roots of many of these errors and rework created have been the adoption of incorrect policies by managers during project implementation. The main goal of the research is to provide a model to reduce errors and rework in construction activities. First, the factors leading to errors and rework in the workshop were identified through the literature and a preliminary questionnaire. After collecting information and statistical analysis, in the next step, the cause and effect model between the variables was drawn through the subject literature and statistical analysis in Vensim. Next, Stock and flowvariables were determined to simulate the hiring policy of temporary workers in the system dynamics model. The statistical population of the research was specialists and experts in the civil phase of oil and gas projects. The findings showed that policies and incorrect decisions of managers based on the mental model can be effective on many errors and rework in projects. The causes affecting the creation of errors and review of the rework created in the projects were identified through the subject literature and questionnaire. The cause and effect relationship of effective variables was done through system dynamics and then drawing state and flow diagrams, appropriate management solutions, to reduce the number of errors. According to the results, hiring temporary workers to increase the progress of the project is one of the things that lead to more errors in the project, which leads to more rework. Education is one of the best ways to get out of this unfavorable situation.