Abstract: In the initial stage of gas reservoir development, water invasion recognizing is significant for preventing water producing and increasing recovery efficiency. In offshore oil and gas reservoir, exploratory and production wells were rarely drilled at the margins of gas reservoirs during the exploration period or the early stage of production.Therefore, after production, some gas reservoirs which have no obvious edge water influence in the early stage would be wrongly recognized as constant volume gas reservoirs, and gas production rate would be increased blindly, which leads to edge water advancing faster. When the edge water starts to affect gas well production, the situation is often not optimistic. In this paper, by analyzing the results of unstable well testing, the gas-water interface is determined and an example of well X-3 in an offshore gas field is discussed. Consequently, a reasonable method for judging the water intrusion status before water breakthrough in a edge water gas reservoir is studied. For gas reservoirs with no water, the water-gas relationship could be recognized so as to configure a reasonable gas production rate. Finally, the advancing rate of edge water would be slower, and both of stable production period and recovery efficiency will be increased.