In order to research the stress -strain constitutive relationship model of concrete confined by steel-frame polyethylene plastic composite pipe(SRPE) under uniaxial compression, the restraint effect of the SRPE pipe on the core concrete is equivalent to the linear superposition of the restraint effect of the outer HDPE pipe and the embedded steel mesh skeleton mid-latitude wire on the core concrete. By referring to the research idea of the classic Mander model, the effective lateral constraint stress of SRPE pipe on core concrete was calculated, and the calculation method for the ultimate compressive stress and strain of SRPE casing concrete is proposed by modifying the strength of confined concrete in the model to increase the coefficient k value, and the corresponding stress-strain relationship model is established. The results show that the calculated results of the model are relatively close to the experimental results, indicating that the proposed constitutive relationship model has a certain accuracy.