This paper proposes a simulation-based optimization technique for the design of a retouch line, consisting of several adjustment and repair sections in an automobile assembly factory. In assembly shops, after finishing the assembly operations in the main line and signing off the automobile, it enters the retouch line in order to be adjusted and repaired if required. There are several stations to fix the probable defects that the product may have. Since the defects and the time required to fix them are stochastic parameters and there are recursive flows between the stations, it is crucial to study and optimize the number of the work stations and the buffer stations. In this study, the retouch line for production of Logan in ParsKhodro Company is simulated by Arena software. Finally, the best number of facilities and stations is suggested by solving the optimization model.