Floorplanning is a key step in the physical design of Very Large Scale Integrated (VLSI) circuits. It is a multi-objective combinatorial optimization and has been proved to be a NP-hard problem. To solve this problem, a coevolutionary multi-objective particle swarm optimization (CMOPSO) algorithm is proposed in this paper. The algorithm imports the concept of coevolutionary algorithm and elitist strategy into basic PSO algorithm, takes both the layout area and total interconnection wire length into consideration simultaneously. Experimental results showed the new algorithm can achieve a better performance.