Abstract: It is necessary to conduct mesh optimization after generating Delaunay mesh, which is essential to ensure the reliability of numerical simulation. To improve the quality of Delaunay mesh on the plane domain, a mesh optimization algorithm based on deep Q network(DQN) is proposed. Firstly, the quality of the initial mesh is evaluated, and the element nodes that do not meet the quality requirements are selected and arranged in ascending order of their quality. Secondly, the node movement is described as Markov decision process, and the DQN model is established and trained. Thirdly, the empirical parameters of the model training are used to accelerate the optimal mesh quality. Finally, several test examples from practical tunnel,cylinder block, mechanical parts, etc., are employed to verify the applicability and reliability of the proposed algorithm. Compared with the existing typical algorithms, the test results show that the proposed algorithm can significantly improve the quality of poor elements, the quality distribution of optimized mesh will be more concentrated, and no invalid elements are produced during the optimization process.