Abstract: Currently the analysis of allowable drift ranges of deepwater drilling dynamic positioning platform is entrusted to foreign professional companies. The calculation process is often poorly confidential and the results not complete. Based on the analysis of operating risks in deepwater drilling dynamic positioning platform in the South China Sea and the zoning of precautionary areas for platform drifting, a practical calculation method of allowable drift range is built by allowing for the physical extreme limits of elastic joint and expansion joint of riser on deepwater drilling platform, the emergency release program, and the operating experience. The method can fully calculate the allowable drift ranges of platform limit release, red circle, yellow circle and green circle. The calculation results have been recognized by platform managers and owners and have been successfully applied in dozens of deepwater wells in many drilling platforms at home and abroad, effectively ensuring the operating safety of deepwater drilling dynamic positioning platform. This record supports the future promotion and application of the method in deepwater drilling practice in China.