Intrapulse quenching of a hydrogen thyratron could be explained with several theoretical methanisms from different viewpoint. It sets a definite on the pulse width and the current of thratron, and results in instable operation. It has been observed that there different phenomena of the quenching for different conditions. Under normal operation conditions, the ignition delay and jitter will gradually increase in course of its operation, at the sama time the positive remaining voltage on the PFN will appear evidently and instably without increased reservoir voltage if a positive mismatch ia established. While hydrogen pressure reduces beyond a certain limit, the pulse missing named pulse to pulse quenching will occur and operation will be very instable. Some oscillograms are given.