Abstract: A eriterion of tesor mullinomial of strength is thcoreliualy analysed and the strength envelopes of laminates with different F₁₂ are given.The effect of F₁₂ on tire envelopes is shown and a method to determine interaction coefficient F₁₂ is proposed.The criterion is verified with two experiments.The results show that Tsai-Wu criterion of tensor multinomial is in excellent agreement with theoretical values in the tension-shear space.And the values from the experiments are in agreement with the tension-shear space.And the values from the experiments are in quadrant 1 and 4.