Abstract: China has been a multinational country from time immemorial。In Qing dynasty,because the foreign powers meddled in the affairs of minority nationalities in frontier regions, the contradictions between different nations changed their intrinsic nature。This paper studied the complicated situation of Northwest China in the early part of the 18th century,and points out that Tsarist Russia was the main supporter of splittings of Dzungar (a tribe of Mongol).In consequence the conflicts between Qing and Dzungar became acute and quite different from the frontier clashes in the past ,therefore the efforts of Qing government to unify China had the implication of resisting foreign aggression.