Abstract: Friction stir welding was carried out on 2mm thick 30CrMnSiA high-strength steel in different heat treatment states.The welding parameters are as follows: rotation speed is 250r/min, welding speed is 30mm/min. The test plates were subjected to pre-welding heat treatment, post-welding heat treatment and non-heat treatment. The results show that heat treatment can significantly improve the mechanical properties of welded joints. Especially the pre-welding heat treatment process, the pre-weld heat treatment process results in a high-strength martensitic organization with the smallest pre-weld grain size of any process under the same conditions, which results in higher strengths in tensile tests; The post-weld heat treatment due to the more plastic ferrite, can also show high tensile strength.