The Deepwater semi submersible production and storage platform and steel catenary riser(SCR) system have been applied for the first time in China in ‘Deep Sea No.1’offshore gas field. The riser system layout is affected by many factors, such as wave, current direction and the access direction of underwater gas wells. Under different layout schemes, potential riser leakage will have different effects on semi submersible platforms and living quarters. Layout of two 12 inch production risers has been analyzed to evaluate the safety risk impact of risers on Living Quarters.Results show that when risers are hanging the west side pontoon of the SEMI, the resulting frequency of impairment is significantly lower for the case with risers on the west side of the platform,while both of the two layout schemes meet the acceptable risk standard. ‘Deep Sea No.1’offshore gas field adopts high-level safety strategy,the 323.9mm outer diameter steel catenary risers are hung off on the west side pontoon of the semi submersible platform. H60 explosion-proof wall is used in the living quarter, the leakage alarm system, abnormal production pressure alarm and shutdown system, mobile safety management system and safety fire-fighting system are comprehensively adopted to ensure the safety of the first deep-water self operated gas field in China. The relevant practice can provide reference for the layout design and risk assessment of oil and gas riser system of other deepwater development projects in the South China Sea.