Abstract: The idea on vassal states and its evolution created great influence on Chinese territory in the Qing Dynasty.Monarchs  of  the Qing had their own understanding on Chinese boundary during the unification.They politely refused the requesting of some vassal states such as Sulu to incorporate into the Qing,while when the disputing on boundary occurred，the Qing ceded some territory to its vassal states.After 1840,China defended strongly its its vassal states invaded by the imperial forces.Facing the imperial forces’ plan to carve up some Vassal States,the Qing court had different opinions .After the breakdown of the suzerain-vassal system,China strengthened its ties with the former vassal states. During the negotiation on the boundary，the patriotic officials strived to regain the territory ceded by the early Qing to it vassal states,but the Qing lost much territory in the end.