Abstract: In view of the in situ repairing requirements of rotor journal of power plant equipment, a non preheating single-layer and multi-passes additive depositing 316L alloy was achieved on 20Cr2NiMo steel by Micro Plasma Arc Depositing process. The microstructure, hardness, chemical composition and mechanical properties of deposition and heat affected zone were analyzed. The results show that the deposition is metallurgical bonded with the substrate, and there is no crack in the cladding layer and heat affected zone; the microstructure of 316L deposition consists of austenite + δ ferrite, and the primary heat affected zone can be divided into decarburization zone, coarse-grained zone, fine-grained zone and mixed crystalline zone, and the primary coarse-grained zone is coarsened, refined and softened due to the secondary heat cycle. The difference of hardness between 316L deposition and substrate is small, while the hardness of primary coarse-grained zone is the highest, but that of secondary coarse-grained zone below 476HV0.3, and the width of heat affected zone is about 2.5 mm; the shear strength of heat affected zone is higher than that of substrate, but the plasticity of substrate is better.