A finite element based progressive damage model is presented for predicting the mechanical response of PE/PE thermoplastic composite laminates. The nonlinear properties of unidirectional PE/PE composites in the longitudinal, transverse and in-plane shear directions were considered as piecewise linear-elastic properties, based on experimental results. Damage accumulations in the laminates were evaluated by using Hashin's failure criteria combined with a proposed property degradation model. The finite element model was implemented into ANSYS software and the progressive failure of UHMWPE/LDPE laminates was investigated. Damage modes such as matrix cracking, fiber-matrix shear-out and fiber fracture were revealed and the damage propagation was presented by the model. Analytical prediction showed excellent agreement with the experimental data.