Based on the component analysis and microstructure observation of Q460 high strength steel with thermo mechanical control process (TMCP), its hot crack and reheat crack sensitivity by using experience formula are evaluated in this paper, as well as its cold crack sensitivity by using implant test is evaluated. The research results show that the content of alloy elements is decreased in TMCP Q460 steel, such as carbon, and the welding and reheat crack sensitivity are both significantly reduced due to the strength improvement by grain refinement. Therefore, the steel’s welding doesn’t need preheating due to the low cold crack sensitivity.