Considering cooperation of workers, this paper develops a multi-objective optimization model of a line-Seru conversion problem to minimize the make span(MS) and the total labor hours(TLH), and applies the NSGA-II-based algorithm to solve the model. Numerical experiments are conducted to testify the necessity of considering cooperation relations. At the same time, this paper evaluates how the variation of the mean and variance of cooperation coefficient influence the system performance. The results show that the performance of line-Seru conversion is improved by the higher mean value and higher variance of cooperation coefficients.