In this paper, a KKS multi-field coupled phase field model for seawater ice crystal growth is established by using the phase field method. The concentration field is selected as the research object, and the governing equation of concentration field is revised based on the adsorption of micro-channel adsorption module and ion exchange resin. The Forward Euler algorithm is used to disperse the phase field and concentration field, and the ADI algorithm is used to disperse the temperature field. The calculation program is written by Visual C++ to solve the governing equations of the phase field, concentration field and temperature field.