Abstract: 20 steel pipes used in ammonia refrigeration system is generally in the state of low temperature and low stress conditions, while only the property at room temperature is considered. To prevent the brittle fracture of 20 steel pipes at low temperature, the ductile-brittle transition temperature (DBTT) is needed to be determined. Charpy impact tests at series of low temperature were carried out to determine the DBTT of 20 steel pipes up to different material standards. The test results of 20 steel pipes up to different standards were compared and discussed. The results show that: the ductile-brittle transtion temperature of 20 steel pipes up to different domestic material standards was between -15 ℃ and -25 ℃, which could be referenced to set the lower limit of using temperature.