Abstract:Cold- formed structural hollow sections steel SS490B is one of the grades of Ti- microalloying export products, which is produced after the cropping of the hot- rolled coil. And it has very strict requirements for the quality of the steel plate. If the property of the steel plate is unstable, the flat form machining flaw will occur in the subsequent process, which can affect the application of customs. According to the production line of FTSR in Tongsteel, the influence factors of the property stability of SS490B steel were analyzed. Based on the analysis results, the property fluctuation of SS490B steel was minimized by reducing the composition fluctuation, improving the slab quality, optimizing the rolling temperature, optimizing the cooling process, stabilizing the laminar cooling, adding the blowing equipment and formulating the corresponding supervision system, which can meet the demand of customs.