Abstract: Based on the small cavity volume of fuel elements in heavy water reactors, this paper designed the measurement equipment to measure the fission gas released by fuel elements in the heavy water reactor, and studied the measurement technology of fission gas release, puncturing technology, measurement technique of fission gas and the pressure sampling technology of fission gas. The technological process and parameters were confirmed. By pressure test and accuracy measurement, this experiment verified the system sealing and volume measurement, established a technique for measuring the fission gas of fuel elements in heavy water reactor and realized the measurement of the fission gas of fuel elements in heavy water reactors.