The project aims to study the tensile mechanical properties of polyethylene foam and construct its constitutive model under tensile. The universal material testing machine is used to perform uniaxial tensile tests on polyethylene foams of different densities at different tensile rates, and the tensile stress-strain curves of the polyethylene foams are obtained; Based on the Sherwood-Frost phenomenological constitutive model frame, a tensile constitutive model of the density term coupling density and strain and the strain rate term coupling strain rate, strain and density are constructed. The tensile properties of polyethylene foam before fracture are nonlinear elasticity, showing obvious strain rate correlation. The existing density term and strain rate term have low fitting accuracy with experimental data, and the maximum average error can reach 11.76% and 7.90% respectively. The newly constructed density term and strain rate term have better fitting accuracy with the experimental data, and the maximum average error is 1.17% and 1.92% respectively. The constructed tensile constitutive model can more accurately describe the stress-strain relationship of polyethylene foam under uniaxially tensile, and provide a reference for further research on the mechanical properties of polyethylene foam.