A method is provided. The method includes: obtaining a parameter value of a determined dimension parameter, an initial parameter value of a dimension parameter to be optimized, and a target capacitance value of an interdigital capacitor; partitioning a geometric structure of the interdigital capacitor to obtain a plurality of sections of the interdigital capacitor, where the plurality of sections are in a one-to-one correspondence with a plurality of coplanar multiple-transmission line models; obtaining a capacitance value expression of the interdigital capacitor based on the plurality of coplanar multiple-transmission line models; determining, based on the parameter value of the determined dimension parameter, the target capacitance value, and the capacitance value expression of the interdigital capacitor, a loss function including the dimension parameter to be optimized; and optimizing, based on the initial parameter value by minimizing the loss function, the parameter value of the dimension parameter to be optimized.