Abstract: Narrow strip steel was used to make the frame tubes. The crack occurred to Q195 when frame tubes were formed. The cause of frame tube cracking is studied by the means of scanning electron microscope,OM,EDS. The result shows that the reason of frame tube crack is Fluxes involved,silicate inclusions Excessive,welds tissue overheating and the degree of cold work hardening is high. It aimed at the crack of different way to research and put forward some measures to improve. Many rectification measures like optimizing the steelmaking process,cooling process after rolling and the welding process were proposed according to the researches on various crack modes. Finally,the crack defect frame tube was effectively controlled. The crack defect rate was reduced from initial 25.5% to 2.7%,which led to the improvement of the yield.