When the deepwater wellhead works in deepwater environment, continuous ocean current movement and accidental collisions will change its local stress state, causing fatigue damage or deformation, which restricts the long-term efficient and safe operation of the oil and gas well. In order to study the steady state and transient dynamics of the wellhead in deep water environment, this paper applies the finite element method to carry out the simple harmonic vibration response analysis and low velocity impact dynamics analysis, and obtains the equivalent force distribution law and time range change law of the deepwater wellhead. The results show that under the influence of the cyclic force transmitted by the sea current and the water barrier pipe, the stresses at the shoulder of the seating and placing platform of the wellhead are more concentrated, which is a potential location for fatigue failure; when the wellhead is subjected to impacts, the impact zone and the shoulder of the seating and placing platform will show a significant increase in stress, which is a high-risk area for structural damage. This study provides theoretical support for the optimal design and damage monitoring of deepwater wellheads.