In recent years, composite materials have been widely used in aerospace and other engineering fields. In actual use, the mechanical properties of composites will change significantly in different hydrothermal environments. There have been a large number of experimental studies at home and abroad in response to this problem, while less research has been conducted on the constitutive model theory of composites in different hydrothermal environments. The study of the thermal properties of composite materials is adopted to introduce the concept of hygroscopic expansion coefficient and thermal expansion coefficient on the basis of classical laminated plate theory. We have established the functional relationship between the elastic constants and the thermal parameters of the materials through the definition of a dimensionless temperature, deriving the constitutive equations of the single layer of composite material under the coupling of moisture and heat. Meanwhile, the 3D Hashin failure criteria has been used to simulate the damage evolution and failure mode of the composite laminates. The results show that the model can predict the elastic response of composite laminates in different moist and thermal environments, which provides an important reference to analyze the mechanical behavior of composite material structure in hydrothermal environments.