Abstract: In order to study stress transfer and damage evolution of single fiber composite in the process of unidirectional loading, a three-dimensional numerical analysis model of progressive damage process based on shear-lag model was established. The curves of single fiber composite progressive damage process, fiber segment, strain load and fiber axial stress distribution at the critical state are in good agreement with the test results in reference, which show that the model established in this paper could effectively simulate damage initiation, damage evolution and critical fracture state. The influences of constituent modulus and strength on damage process were also researched. The results show that increasing fiber modulus can speed up the damage process while maintaining constituent strength unchanged, and the increasing matrix and interfacial modulus have little effect on progressive damage process. Maintaining modulus of constituent materials and interfacial strength unchanged, with the increase of fiber strength, both the initial and critical strain load of single fiber composite progressive damage process increase, and the fiber breaking point at the critical state reduces.