The work aims to improve the comprehensive properties of the laser-cladded martensite stainless steel (MSS) coating. Fiber laser was utilized to prepare 420 MSS coatings on Q235 steel substrate by continuous scanning and idle scanning (the laser was switched off 30 s between layers), respectively. The microstructure, mechanical properties and corrosion resistance of the coating specimens prepared by different laser scanning modes were characterized by equipment such as X-ray diffractometer (XRD), scanning electron microscope (SEM), universal material testing machine, Vickers microhardness tester and electrochemical workstation. The microstructure of the continuous scanning specimen was uniformly distributed, mainly composed of martensite (M) and a small amount of residual austenite (Ar), exhibiting brittle fracture with the tensile strength of 1368 MPa and elongation of 3.91%. The idle scanning specimen consisted of two different types of microstructure due to the in-situ tempering effect. One was the fine gray microstructure, accounting for 89.8%, which was composed of tempered martensite (Mtmp), dispersed-distributed D23C6 particles (D was Fe, Cr, etc.) and a small amount of Ar. The other was coarse bright white microstructure, accounting for 10.2%, which was mainly composed of un-tempered M. The idle scanning specimen exhibited the tensile strength of 1694 MPa and elongation of 12.46%, but the microhardness and corrosion resistance slightly decreased. The strength and ductility of the laser-cladded 420 MSS coating can be significantly improved by in-situ tempering effect.