Abstract: In the course of pipeline transportation of condensate gas, wet gas often occurs to the behaviors of retrograde condensation due to the changes of pressure and temperature along the pipeline, so its flow belongs to the category of low liquid holdup two-phase flow, and the process calculations are not in correspondence with usual natural gas pipeline. According to the transporting feature of submarine pipeline, the theoretical studies including flow regime prediction, establishment of hydrodynamic and thermodynamic models and computer modeling of different technological calculation methods are conducted in the paper. And meanwhile the steady computer programs for technology calculation are developed. The reliability and precision of the models are demonstrated by comparing with producing data of JZ 20-2 and Pinghu-Shanghai offshore pipelines, and the relative derivation between the results of models and the same kind of foreign software PIPHASE & HYSIM are all within 10%. The example analysis indicates that computing results with a high relatively accuracy are obtained with the calculating models proposed in this paper, and these models can simulate the change laws of pressure drop, temperature drop, liquid holdup and velocities of gas and liquid along practical producing pipeline. In the aspect of judgment of hydrate forming zones and flow pattern prediction, the validity of the method are verified, but the calculating value of accumulated amount of liquid in the pipeline is smaller.