Based on the accumulation of He in gas reservoirs, we show how physical model of determining the formation time of gas reservoirs be developed by learning the other dating model. Introduced the parameter of the gas reservoirs in this model, both radiogenic He from crustal flux and in situ He production was calculated. Considering to time-accumulating effect of the He, the age of the gas reservoir formation was derived. We use this approach for Weiyuan gas reservoir in SIChuan basin. The calculated He age is 31Ma, which is consistent with the analysis of gas formation and accumulation history，this result indicate the model of He accumulation can be used to study the formation time of gas reservoir.