In the process of collaborative product design, each participating member from different companies has his own interest and is not always willing to make concession; therefore, the conflict management is an inevitable and important task. This research presents a negotiation approach with the Particle Swarm Optimization (PSO) method to resolve the conflict problem between designers in order to find the optimal design parameters with the highest joint utility. This study takes the design of spur gear as an example and the negotiation issues are material, price, quality, modulus, number of teeth for driving gear, and coefficient of gear face width. This study also uses the Genetic Algorithm method to go through the same process as PSO, and then we compare the effectiveness of resolving the conflict problem in collaborative product design between two methods.