The influence of the mixing time of Pd(II) and Rhus vernicifera laccase on the oxidation of 5,6-dibromo-2,3-dicyanohydroquinone (DDBQH2) catalyzed by laccase has been studied through spectrophotometer at pH 4.5 and (30 +/- 0.1 degree C). The activation of Pd(II) on the laccase activity is gradually converted into inhibition and ultimately inactivation with the extension of the mixing time of Pd(II) and laccase, and the rate of such conversion goes up with the increase of Pd(II) concentration. The influence of Pd(II) on the absorption spectrum of laccase suggests that it is the type I site in laccase with which Pd(II) interacts and Pd(II) may gradually and at last substitute Cu(II) from the site. The substitution may be the cause of decrease and disappearance of laccase activity.