In order to explore and establish the mathematical model of the greater interlaminar stress at the internal interface of the part caused by the mismatch of the thermal expansion coefficient between the metal and the composite during the forming process of the fiber-reinforced metal laminate. First of all， in order to simplify the mechanical model of fiber-reinforced metal laminates reasonably， through analyzing the influence of the change of three-dimensional anisotropic scale of simple asymmetric fiber-reinforced metal laminates on the warpage degree after forming and demoulding， it is found that the magnitude of interlaminar stress is mainly related to the proportion of metal and composite materials in the laminates. Then the mechanical model of the laminated plate is simplified into two-dimensional model by using the obtained law. Based on the analysis of elastic mechanics and theoretical mechanics， the mathematical model of interlaminar stress of unidirectional asymmetric fiber-reinforced metal laminates is obtained. By dividing symmetrical laminates into several asymmetrical laminates， the interlaminar stress expression of fiber metal laminates in asymmetric laminates is successfully extended to standard symmetrical laminates. Because it is impossible to measure the interlaminar stress directly， the theoretical value of interlaminar normal stress will be obtained indirectly based on the relationship between interlaminar shear stress and interlaminar normal stress. The stress value measured by the fiber grating sensor is compared with the stress value obtained by the theoretical model， and the maximum error does not exceed 3.504%， which verifies the accuracy of the theoretical model of the interlayer stress of the fiber metal laminate.