Abstract: The poplar fiber/polyethylene composites with different contents of poplar fiber were prepared. The micromechanics of poplar fiber/polyethylene composites were modeled by Hirsch model, Kelly-Tyson model and Bowyer-Bader model. By studying the tensile stress-strain curves of the poplar fiber/polyethylene composite and plastic matrix and the length distribution of poplar fiber in the composite, the orientation coefficient, interfacial shear strength and intrinsic tensile strength of poplar fiber in polyethylene matrix were calculated, and the variation law of the tensile properties of poplar fiber/polyethylene composites was explained. In addition, the contribution ratio of subcritical fiber, supercritical fiber, plastic matrix to the tensile strength of poplar/polyethylene composites was obtained by using micromechanical model calculation.