Abstract: The deepwater surface soil is loose and soft, the pipe is lowered by ejection generally, and the wellhead radial stability performance is weak. In particular, when the subsea geology of well exploration in the deepwater new block is not clear and the intensity parameters of superficial layer soil are inaccurate, the radial stability of underwater wellhead is especially important. In order to improve the stability of radial load of underwater wellhead, based on the wellhead sinking of surface casing during the circulation before cementation and during the cementing period in the site operation, the radial stress of pipe during the surface casing cementation period is analyzed; furthermore, according to the site operation practices, the method for wellhead sinking prevention has been raised and successfully applied in the operation practices. It improved the stability of radial load of underwater wellhead, effectively promoted the smooth and safe deepwater surface layer operation, and guaranteed the safety of deepwater drilling.