Abstract: At present，the control of steel pipe circumference accuracy is basically carried out at the formation station in the HSAW pipe production line. However，due to the narrow space of the forming station，it is not possible to install relatively complicated measuring device，and in most cases on the site manual circumference measurement has to be used，which causes the problems of high labor intensity and large measurement error. Accordingly an automatic measurement system for weld pipe circumference as installed at the formation station on the production line is developed. Thanks to the said system，on-line circumference measurement of the HSAW pipe at the formation station is realized. The system features small space occupation，high measurement accuracy and effectiveness，having been satisfactory to the application requirement for the circumference measurement at the weld pipe formation station.