The exploration and exploitation of deep-sea oil and gas resources is an important part of China's energy strategy and an inevitable trend of world energy development. As a key equipment for exploration and development, the mechanical behavior of marine pipe strings will directly affect the working performance and safety reliability of testing columns, downhole tools, etc. Based on extensive research on the mechanics of marine pipe strings and the structural characteristics of deep-water test strings, a coupled dynamic model of deep-water test strings based on the deformation effect of risers was established, the model was solved using the characteristic line method and a deepwater test string similarity experiment was conducted to verify the model. Combined with on-site data from a well in the South China Sea, the vibration characteristics of the deepwater test string were analyzed and the vibration variation law of the test string was obtained. The results show that periodic vibrations occur when gas flows through the test string. Notably, transverse vibrations are significantly more pronounced in seawater sections compared to formation sections. Furthermore, within seawater sections, maximum vibration amplitudes are observed in the middle part while within formation sections they are concentrated in both middle and upper regions. Additionally, it is worth noting that lower ends of test strings exhibit larger longitudinal vibration amplitudes as they approach closer proximity to formations. Moreover, amplitude levels experienced by pipes within deformed seawater sections are evidently smaller than those encountered without deformation; furthermore, pipe column vibrations experience faster attenuation rates.