Abstract: Analyzed is the mechanism of effects by the chemical composition and microstructure of the steel strip on the weld property of the HFW pipe. Accordingly，countermeasures are proposed. The analysis result reveals the following facts. The contents of C，P and S，and the grain size of the hot-rolled steel strip have obvious influence on the low temperature impact property；the inclusions and the banded structure of the steel also produce significant effect on the impact toughness of the pipe； and the micro-alloy elements like Nb，V and Ti jointly play a role in restraining growth of austenitic grains during welding and MF heat treatment processes.