Abstract: The article conducted strength tests and analytical research on carbon-carbon composites, aiming to establish a more accurate strength criterion suitable for engineering applications. Initially, a Z050 biaxial mechanical property testing machine from Zwick/Roell was employed to perform biaxial tension, tension-compression, and compression tests. Subsequently, based on the observed changes in failure modes during the tests, a piecewise continuous higher-order tensor polynomial strength criterion was proposed, accounting for different failure modes. The critical point k where failure mode transitions occur in biaxial tests was derived from the perspective of strain energy. By introducing cubic cross terms and ensuring continuity of the strength criterion at the critical point, the specific form of the criterion was determined. Finally, based on completed biaxial tests of carbon-carbon composites, the new strength criterion was compared with the Hoffman criterion and Tsai-Wu criterion, revealing superior predictive performance across all intervals. This criterion is a cubic strength criterion applicable to anisotropic composites, incorporating consideration for diverse failure modes.