Shell diamond film was prepared by DC plasma CVD, and substrate shape had an important influence on the growth of shell diamond film. Simulations of the substrate temperature field have been done respectively when the substrates are convex and concave. The simulation results show that, DC plasma flow more easily on convex substrate than concave substrate, and temperature field of convex substrate is more uniform than concave substrate; uniform temperature field was help to prepare high quality shell diamond film. In this study, shell diamond films were prepared on convex and concave substrate, respectively in experience. The results indicate that the growth of diamond film on convex substrate was better than on concave substrate, and Raman spectrum shows, on the convex substrate, high quality shell diamond film was prepared successfully, and it accords with the simulation results.