Biopolymer gels have many applications in tissue engineering. In recent years, biopolymer gels are widely used as scaffold material in the 3D bioprinting technique for tissues and organs. To optimise the printing process, it is important to study and understand the temperature-and time-dependent gelation kinetics of biopolymer gels.In this study, a thermodynamic model is proposed to describe the gelation kinetics of thermoreversible gels, which are driven by the coil-to-helix transition. In this model, the gelation process is assumed to proceed in two steps. The process starts from the reference state, in which the solution consists of solvent molecules and polymer chains with n segments in random coil configuration. Polymer chains firstly change from the random coil state to the partially helical state, followed by the aggregation of helical parts of polymer chains. This formation and the followed aggregation of helices lead to the eventual polymer network. With the help of the phase-field method, numerical simulations of a spatial and time varied gelation process of droplets in 3D bioprinting are performed using the finite element method (FEM).