The purpose of this research is to solve stress calculation problem of the composite pipe of multihole steel pipe and polyethylene of raised temperature (PE-RT). The formulas, used to calculate the burst pressure of the composite pipe, were established separately based on three kinds of different strength theories, and also the formula, used to calculate axial stress was developed based on the deviator strain energy theory. The calculation results were compared with the measured values. It shows that the calculation results of formula based on the deviator strain energy theory are very close to the measured values. This conclusion has important meaning to the heating directly buried installation of the composite pipe.