Abstract: Reservoirs in the Tahe Oil Field are carbonate karst ones with active bottom water and strongheterogeneity.In the past years,oil field descent rate was over 25%.Reasons for the descent were clas-sified.From the aspects of geology,accumulation and oil recovery process,the main factor for the de-scent was found.Descent control considering different factors was carried out,reducing descent rate andimproving oil field exploration effect.