The paper mainly discusses the association relation and evolution sequence ofthe Northwest Pacific island arcs and puts forward the mode of motion of the Pa-cific plate. Each island arc in the Northwest Pacific island arc system is composed ofcontinental crust arc and oceanic crust arc (except for the Mariana island arc). Thecontinental crust arc is a part of continental crust separated from continental mar-gins oceanwards when a back-arc basin was formed. It is located on the concave sideof an island arc. Each continental crust arc has a complete shape. Its left end(thefront is the convex direction of the island arc) joins the continent, while its rightend is cut by a late-formed adjacent island arc. The oceanic crust arc was formedin the process of subduction of oceanic crust. It is melange resulting from mixingof continental and oceanic crustal materials. It, parallel to a deep trench, is locatedon the convex side of an island arc. The Northwest Pacific island arc system hasevolved from the terminal Mesozoic up to the present. It shows a distinct regular-ity of south-younging.