The current gas relay heavy gas action flow rate calibration values used in actual working conditions are lacking reliability and only provide a certain parameter range as a reference. Therefore, in order to improve the sensitivity of a heavy gas alarm, this paper proposes a method based on the angular velocity of a gas relay baffle rotation. First, it analyzes and derives the angular velocity characteristics of gas relay baffle rotation, and develops an intelligent gas relay with real time output of the rotational angular velocity of the baffle and a gas relay dynamic characteristic experimental platform. This can simulate different heavy gas fault energy magnitudes. Then it tests and analyzes the angular velocity characteristic relationship under different excitations. From the test results, a series of simulation analyses is carried out. The adjustment value of the baffle rotation angle speed is obtained from the test and simulation results. From judging whether the baffle rotation angle speed reaches its adjustment value, it gives a timely heavy gas alarm. This improves the sensitivity of the heavy gas alarm, and provides a new adjustment method for a heavy gas fault alarm. This work is supported by the National Natural Science Foundation of China (No. 51777075).