It is difficult to solve design optimization problems of complex systems by using a traditional computing method because complex simulation processes usually lead to large-scale computation. Therefore the distributed computing technology based on decomposition-coordination theory has received much attention by design engineers. This paper studies a peer-to-peer collaborative optimization method based on distributed computing technology in order to examine flexible optimization. A new distributed collaborative optimization framework is proposed, and a coordination method is developed and used to deal with the conflict of related variables among sub-optimization problems. A multi-agent based distributed computing environment is implemented. The implementation of an optimization agent, in which CORBA technology is used to implement communication between the components of the optimization agent, is discussed in detail. Two examples are used to demonstrate the efficiency of the computing method and the reliability and flexibility of the multi-agent system.