Abstract: Energy internet can improve the energy efficiency and promote renewable energy accommodation by complementarily utilizing multiple energy resources and coordinating optimization, which is of great economic and environmental significance. Natural gas, hydrogen and etc., the core elements of energy internet, can be transferred through pipelines under the physical regulation（such as Weymouth equation, Panhandle A equation, Panhandle B equation）. However, the nonlinear gas equations bring some challenges to the energy flow computation. To address this issue, the nonconvex nonlinear gas equations were isomorphic to a tractably convex optimization model, whose optimal solution can precisely satisfy the gas flow equations of pipelines and pressure equations of compressors. Furthermore, a piecewise linearization technique was used to linearize the nonlinear objective function of the model, thus transforming the original model into a linear programing model. Multiple natural gas networks and hydrogen networks were selected as the test cases. The optimal solutions were given to verify the feasibility and effectiveness of the model. The number of segments on the accuracy and efficiency of the solution was analyzed.