  A symmetry-preserving regularization procedure for dealing with the contact
interaction model is proposed in this work. This regularization procedure
follows a series of consistency conditions which are necessary to maintain
gauge symmetry. Under this regularization, proofs for the preservation of the
Ward-Takahashi identities are given and the loop integrals in the contact
interaction model are systematically computed. As an application example, the
kaon electromagnetic form factor and $K_{l3}$ transition form factor are
computed and self-consistent results are obtained. Since the proposed
regularization properly handles the divergence, one is freed from the
inconsistencies caused by the regularization and can concentrate more on the
physical discussion.
