In this paper, selective laser melting thermal stress of 316L stainless steel materials was studied, and real-time stress monitoring platform was established. The change discipline of thermal stress, correlation between temperature and thermal stress, change discipline of scanning thermal stress of SLM finished single-layer multi-channel and multi-layer single-channel were discussed, and the change of thermal stress under varied craft parameters was further studied. Results show that in the process of selective laser melting, the change of thermal stress includes four stages: press, pull, offsetting of press and pull, balance of pull and press, and the final residual stress is pull stress; the change altitude of thermal stress is negatively correlated with scanning speed, and positively correlated with laser power. However, slow scanning speed led to remelting in the process of melting and made residual stress released.