In order to explore the key technology of oil and gas drilling in Marine sedimentary strata in lower Yangtze area,the drilling technology of well 1 of Wanyoudi is discussed. Especially the interactive existence of collapse prone strata, gypsum layer and fracture leakage layer, and the construction technology under the condition of narrow drilling fluid density window. Through the study of drilling technology under complicated working conditions in this area, a set of suitable wellbore stability control method, gypsum layer bit balling treatment method and drilling method under the condition of narrow drilling fluid density window were formed to ensure the completion of this well. It provides reference for the next drilling operation in this area.