  We have investigated the present renormalization prescriptions of
Cabibbo-Kobayashi-Maskawa (CKM) matrix at one-loop level. We emphasize at one
prescription which is formulated with reference to the case of no mixing of
quark's generations and point out that it doesn't make the physical amplitude
involving quark mixing ultraviolet finite. We then propose a revised
prescription to solve this problem and simultaneously keep the unitarity of the
CKM matrix. Through explicit calculations we also prove that in order to keep
the CKM matrix gauge independent the unitarity of the CKM matrix must be
preserved.
