In order to study the effect of different inner tube radius, fin length and fin thickness on heat storage of tube-fin phase change heat storage device, a reliable and fitting regression equation was established by using the method of orthogonal test combined with numerical simulation, and the three factors were optimized. The test results show that the three factors all have obvious influence on the heat storage device. The influence degree on the heat storage, from large to small, is the fin length, the inner tube radius and the fin thickness, and the interaction of the three factors will also have a certain influence. The regression equation satisfies the significance test and the misfitting test. To test the accuracy of the equation, an arbitrary set of data is given, and then the error of the equation is only 0.2%. The regression equation shows that the inner tube radius, fin length and fin thickness is 30 mm, 20 mm and 20 mm respectively when the heat storage reaches its maximum in the period of 5000 s. The research in this paper lays a foundation for the optimization and application of the tube-fin phase change heat storage device. © 2022, Science Press. All right reserved.