In this paper,the welding test pieces were prepared by surf acing the low-alloy steel electrode on S271 plate grooving specimens of nuclear grade low-alloy steel by electrode arc welding manual temper bead technique. The influence of local increase of welding heat cycle on the microstructure and properties of HAZ and the influence of the thickness of tempered surfacing layer on the microstructure and properties of HAZ were studied. And the results showed that,the tempering furnace of the microstructure of the HAZ nearby weld toe was insufficient without increasing the welding thermal cycle;and the impact toughness was bad which caused by the martensitic and the interface of retained austenite in the HAZ,the martensitic was detected,the interface of retained austenite was disappeared,and the impact toughness was improved obviously,while increasing the welding thermal cycle. The tempering furnace of the microstructure was improved obviously by part of layer removed. And the value of the hardness（HV0.2） was reducing and the value impact toughness was increasing,with the increasing thickness of grinding.