Abstract: Carbon fiber reinforced polyether ether ketone (CF/PEEK) is a high-performance thermoplastic composite with broad application in aerospace. PEEK has a non-linear behavior related to temperature and strain rate, which makes CF/PEEK have similar mechanical behavior in plane shear direction. In this paper, shear experiments were carried out on CF/PEEK specimens at different temperatures and strain rates. The stress-strain curve was divided into linear and non-linear parts. It is found that temperature and strain rate have a greater influence on the yield stress of CF/PEEK. With the increase of temperature from 20℃ to 130℃, the yield stress decreases by about 66%, and the rate of decrease is fast and then slow. With the increase of strain rate from 10⁻⁵ s⁻¹ to 0.1 s⁻¹, the yield stress increases uniformly by about 35%. This phenomenon is fitted into an empirical formula of back stress, and the yield function of the classic elastoplastic constitutive model of thermoplastic composites is modified, which is applied in VUMAT to analysis the shear behavior of CF/PEEK. Compared with the experimental results, it is found that the yield point and the nonlinear stage are in good agreement. However, due to the poor infiltration of fibers and PEEK matrix, CF/PEEK composites have porosity defects inside, which affectes the initial elastic behavior of CF/PEEK composites and resultes in the deviation in the initial loading stage.