This paper establishes a longitudinal, transverse, and torsional dynamic analysis model for deepwater drilling strings, considering the bit-rock interaction, and performs calculations to obtain the dynamic response behavior. Miner's linear cumulative damage theory is used to calculate the fatigue damage of the drilling string. The results indicate that the overall stress of the drilling strings decreases with increasing depth, reaching its maximum value at the top of the string. Increasing drillbit, rotational speed, and torque will increase the vibration of the string, with drill bit being the primary factor affecting the vibration. Finally, this paper has engineering guidance significance for ensuring the safety of the string in long horizontal wells in deep water.