Abstract: In order to shorten the design period of engineering systems and improve product quality, and according to computational complexity, coordination disorder and other problems existing in collaborative optimization (CO) algorithm, some ameliorated studies were done in the paper. The Ameliorated Collaboration Optimization (ACO) algorithm was applied unconstrained system level which eliminated the potential for a singular Jacobian, and L1 norm which was used for improving subsystem consistency constraint. In addition, some optimization parameters and constraint models were added in the subsystem. The results from numerical simulation showed that computing efficiency of ACO algorithm was 2.6 times of CO algorithm, and the optimization result was more approximate to the real datum. Furthermore, ACO algorithm was applied to the design of articulated vehicles, fuel economy for vehicle could be improved by 2.596%, and the acceleration time of vehicle from zero to maximum velocity decreased by 6.051 seconds. The results show that the algorithm can help to improve calculation efficiency and accuracy in the optimization design of complex engineering system.