Abstract: Plain Weave Carbon Fiber Reinforced Polymer (PWCFRP) is widely used in engineering fields such as aviation, aerospace, and vehicles due to its uniform in-plane mechanical properties. However, its mechanical properties and failure mechanisms have always been difficulties in application. In order to explore the effects of stress state and strain rate on the in-plane mechanical behavior of PWCFRP, we conducted quasi-static tension, compression, shear experiments and dynamic tension experiments to analyze the mechanical properties and damage mechanism of the material, and based on the Tsai-Wu failure criterion, the failure envelope of the material under multi-axial stress state, different strain rates and different off-axis angles was quantitatively analyzed. The results show that under quasi-static load, PWCFRP shows significant tension-compression asymmetry, and the tensile strength is increased by 120.46% compared to the compressive strength; under tensile and shear loads, the mechanical behavior of PWCFRP is nonlinear. The failure of the material in the tensile state is mainly caused by the tensile fracture of the fiber bundles, and the fracture location shows a certain randomness; the material failure in the compressed state is mainly caused by the kink fracture of the fiber bundles caused by local high shear stress, and the fracture angle is approximately 37°; the failure mode of the material in the shear state is mainly the tensile-shear coupling failure of the resin. Under dynamic tensile load, the tensile strength of PWCFRP first increases and then decreases with the increase of strain rate, with the highest strength value at the strain rate of 2000 s⁻¹. Under the multi-axial stress state, the tensile strength and the significance of the strain rate effect of PWCFRP show a negative correlation trend with the off-axis angle (0°-45°).