The accurate prediction of temperature is the basis for predicting hydrate formation. Presently available methods for the calculation of temperature distributions in pipelines are based solely on the traditional heat transfer mechanism between the high-temperature fluid in the pipeline and the low-temperature surroundings. The influences of hydrate formation and deposition behaviors on the temperature variation have not been considered in the heat transfer process. Hydrate formation is exothermic, and the hydrate layer formed by the deposition of hydrates has a resistance effect to the heat transfer process. In this study, an improved thermal model for predicting the temperature distribution in gas-dominated systems is proposed. In this model, the influences of hydrate formation and deposition behaviors on the variation in temperature are considered. The model is verified by comparing with experimental data from literature. The transient variation in temperature along the pipeline can be obtained using the model. The simulation results indicate that hydrate formation and deposition have a significant influence on the variation in temperature in the pipeline, and can cause an inhibiting effect on the later hydrate formation. This work adds further insight into the heat transfer process and can serve as useful reference for the accurate prediction of temperature distributions in pipelines.