Abstract: The tritium measurement in ionization chamber will be widely used in tritium plant, nuclear fusion reactor, environmental monitoring and various tritium related experimental devices. The gas with certain tritium activity concentration was prepared by PVT. The tritium calibration experiment was carried out by using the flow gas type filament wall ionization chamber experimental system, and the influencing factors were verified by orthogonal experiment, so that the calibration of ionization chamber was completed. The results show that the stability of the ionization chamber is excellent, the relative deviation is less than 1%, the linear correlation of pressure effect is about 1, and the memory effect is less. The calibration coefficient of ionization chamber IC1, IC2 and IC3 is 1.35×10¹⁸, 1.34×10¹⁸, and 1.33×10¹⁸ respectively. It can measure tritium accurately and on-line for a long time and can meet the requirements of tritium measurement in tritium related places.