Abstract: Because the existing shared mental model theories cannot fully adapt to collaborative design and give explicit explanation for mental collaboration, this paper studied the interaction between two evolution processes, named "individual mental models-shared mental models" and "design problem-design solutions", from the perspectives of design and cognition. A cognitive mechanism of "design problem → individual mental models → shared mental models → design results" was revealed. And a design mental collaboration solution model was built based on the shared mental model theories. Firstly, the knowledge and belief of individual design mental models were expressed and induced as two core elements; Secondly, considering factors of sharing degree and individual weight, individual design mental models were integrated into the shared design mental models with the statement as the basic unit; Thirdly, the solution of the design problem was extracted from the shared design mental model. The collaborative design of 3D printer nozzles was taken as an example to construct the shard deign mental model under the guidance of this mechanism, which solved the problem effectively.