Abstract: Fixed ambient dose equivalent radiation ratemeter is widely distributed in the nuclear power plants, for conventional continuous monitoring or nuclear accident emergency monitoring. It is not easy to disassemble the fixed installation and send it to the metrology laboratory for calibration. In order to ensure the accuracy of fixed ambient dose equivalent radiation ratemeter, the Monte Carlo method has been used for the design of ambient dose equivalent secondary standard ionization chamber and portable gamma ray irradiation device, and on-site calibration experiment has been carried out. The on-site calibration factors have been compared to the calibration factors obtained in laboratory, and the results showed that on-site calibration problems can be solved using ambient dose equivalent secondary standard ionization chamber and portable gamma ray irradiation device.