Abstract: To minimize costs and enhance the economic efficiency in the development of the marginal Liuhua 19-5 Gas Field, a new subsea production system is required. Accordingly, the subsea completion technique was investigated. Sand control and string designs were completed for offshore horizontal well completion, and technical measures for prevention of hydrates, scaling and waxing in wellbores were proposed. Moreover, optimal tools and materials for completion tools and string were selected, gas-lift drainage by nitrogen injection with coil tubing was deployed for production, and the emergency response program for drifting of submersible drilling platform was developed. Thus, the new subsea completion technology was formed. It was successfully adopted in two wells in the Liuhua 19-5 Gas Field, with average completion time of 30.32 days. Research and application results showed that the new subsea completion system could enhance production efficiency, reduce operational costs, and realize the effective development of marginal gas fields.