Focusing on the issue that knowledge is not equal in task assignment of product development, a task assignment model of product development based on bilateral matching of task and designer was proposed. Firstly, the matching between task and designer was transformed into the similarity of knowledge between task and designer from the perspective of knowledge quantification, then the order value matrix was established and transformed into the satisfaction degree matrix of task to designer matching. Secondly, according to the degree of preference of the designer to the task under different task attributes, the order value matrix of designer satisfaction to task was obtained. Thirdly, based on the principle of maximum satisfaction between the two parties, a multi-objective optimization model based on knowledge similarity and designer preference was constructured. The method of weighted sums based on membership function was used to change the multi-objective optimization model into linear programming model, then the obtained model would be solved by Matlab programming. Finally, taking a crankshaft linkage mechanism produced by one enterprise as an example, the matching result between four tasks and seven designer was obtained to determine the final assignment plan. By comparing with task assignment methods of product development based on clustering analysis and bilateral matching, the apparent difference between the knowledge similarity and the designer preference between the designer 3 and 7 indicated that the proposed method can assign tasks more efficiently.