Abstract: The 1. 2 mm diameter H08 Mn2 Si welding wire was used as the test material,and the arc welding process was tested by the bypass hot wire plasma arc method,adding material to the aerospace shaft structural parts,and obtaining a good molding effect,the effect of interlayer temperature on the microstructure and properties of additive was studied. At the same time,the microstructure and mechanical properties of the repair joint were studied by optical microscope,tensile tester and hardness analyzer. It is found that with the increase of interlayer temperature during the additive process,the cooling time of the molten pool is gradually shortened,the secondary growth of the grains is more and more obvious,the grains are more and more coarse,and the content of pearlite is also decrease,the tissue near the additive zone is a small pearlite structure,while the heat affected zone is obviously coarse. In addition,the hardness of the additive structure also increases with the increase of the interlayer temperature. After repair,the tensile strength and hardness of the material are higher than the base metal,which meets the requirements for the use of structural parts.