Abstract: It is difficult to transport viscous oil in normal-temperature pipelines because its viscosity is higher at lower temperature. Therefore, it is necessary to apply the electrical heat tracing techniques in those oil pipelines. In this paper, comparative analysis is conducted on existing electrical heat tracing methods including mineral insulated heating cables (MI), skin-effect electrical heat tracing and electrical heating cables, with the focus on MI electrical heat tracing. Optimal design is performed on MI heat tracing volume and temperature control circuit after its compositions and principles are studied, so as to realize isothermal heat tracing transportation of oil pipelines. Isothermal MI technology is practically applied to heat tracing for Laowenquan Oil Pipeline in Tanggula Mountains. It is indicated that the isothermal MI technology can be easily applied to oil pipelines of various viscosities due to its features of lower power consumption, high efficiency, safety and reliability.