Abstract: Temperature drop calculation in a multiphase pipeline is based on pressure drop calculation and it is very important to devise heater and learn about gas and liquid equilibrium. Temperature drop calculation in a multiphase pipeline is different from that of a pipe in gas or liquid alone. Mixture of gas and liquid discharges heat into the atmosphere, and cause energy and mass exchange. So far, it has no good ready-made formula to calculate temperature drop. According to conservation of energy, when Joule-Thomson effect on natural gas and friction heat of liquid are considered, a temperature drop formula to calculate multiphase pipeline is deduced. After undulation of pipelines effects on temperature drop is taken into account and mass void gas is replaced by liquid holdup, the formula will be better agreement with field data.