Mostenvironmentalissuesandpolicydesigningareuncertainandirreversible;therefore,thetimingofenvironmentalpolicyimplementationbecomesespeciallyimportant.Thispaperestablishesarandomdynamicprogrammingmodelandanalyzestheoptimaltimingproblemsinenvironmentalpolicyunderuncertainvariables.Thismodelresultsindicatethattwovariableshaveasignificantimpactonthetimingofenvironmentalpolicyimplementationandtheyworkinoppositedirecfons:ononehand,themoreuncertaintheeconomyis,thehigherthecostofpoliciesimplementationwillbe,andconsequentlytheincentivetoimmediatelyadoptthepolicywillbestronger.Ontheotherhand,thehighertheuncertaintyoftheenvironmentis,thestrongertheirreversibilityofecologicalharmcausedbypollutantsperunitwillbe.Therefore,thegovernmentshouldimplementnewenvironmentalpoliciesasearlyaspossibleinordertogainmoreecologicalbenefits.
