The deepwater subsea wellhead is the main load-bearing component, in order to study the reliability of the wellhead structure in deepwater environment, a finite element model of the wellhead was established. Static analysis was carried out of the wellhead, the main structural parameters were determined using response surface method, and reliability analysis was carried out on the wellhead based on the Six Sigma criterion. The results show that the maximum total deformation of the wellhead occurs at the connection with the upper device, and the maximum equivalent stress occurs at the contact position with the support ring; when the reliability is 0.99996, the maximum equivalent stress is 634.25MPa, which is less than its allowable stress, and the sigma level is 3.88, indicating that the structure is stable and reliable.