This paper researched on the outsourcing service contest with decision preference and difference of decision order, and through building the contest model of the outsourcing service contest with decision preference and difference of decision order, it probed into the influence of decision preference and difference of decision order on the equilibrium service level of suppliers, total equilibrium service level and average service level acquired by the purchaser in outsourcing service contest. And the result demonstrates that when there is difference of decision order, although the decision preference of suppliers could affect the contest equilibrium, and revise the influence of difference of decision order on contest equilibrium, and when there is decision preference, the difference of decision order of suppliers will have bad effect on outsourcing service contest.