This chapter is devoted to introducing some basic constitutive models of fiber reinforced plastics (FRPs), presenting the rationale for modifying and improving the constitutive model in accordance with the actual physical mechanism, and proposing the application ideas of the constitutive model for material subroutines in conjunction with the finite element (FE) method. These constitutive models can serve as a foundation for the establishment and development of new constitutive models. As we know, the advent of fiber reinforced plastics (FRPs) has furnished robust reinforcement for aerospace and other sophisticated equipment, thereby facilitating and enhancing human exploration of the sea, land, air, and sky. This kind of material has the characteristics of multi-phase distribution, which allows artificial control of its properties, qualifying it as an advanced composite material. However, as the scope of FRP applications continues to expand, a number of new challenges have emerged, including those related to physical fields, boundary conditions, material limitations, and more. This underscores the necessity for further development of some existing theories. Finite element analysis (FEA), as the third paradigm of scientific research, has been instrumental in facilitating significant advances in numerous engineering design projects. At present, the application of FEA to FRPs remains a complex, time-consuming, and pivotal process, which suggests that this chapter will provide useful insights.