Threshold correction on gaugino masses at grand-unification scale

We calculate the threshold correction on gaugino masses of the SU(3)\ifmmode\times\else\texttimes\fi{}SU(2) \ifmmode\times\else\texttimes\fi{}U(1) gauge group at the grand-unification scale in SU(5) supersymmetric (SUSY) grand unified theory (GUT). This depends on the content of the heavy chiral multiplets and the pattern of their soft SUSY-breaking mass parameters. We show that in the minimal SU(5) SUSY GUT the correction to the GUT relation of the gaugino masses is very small as long as all the soft SUSY-breaking mass parameters are of the same order of magnitude. Also, we discuss the correction of the GUT relation of the gaugino masses in the nonminimal models and show that the GUT relation of the gaugino masses can be broken only in some special circumstances.