The invention provides a quick closing mechanism of an isolating switch and the isolating switch with the quick closing mechanism. The quick closing mechanism of the isolating switch comprises a moving contact support with a moving contact, a static contact support with a static contact, an operating handle, a connecting rod, a sliding groove, an elastic driving piece and a quick closing piece. The quick closing piece is hinged and extends to form a limiting step, the moving contact is arranged at a first end of the moving contact support, a first end of the moving contact support further extends to form a hook portion corresponding to the limiting step, the elastic driving piece acts on a second end of the moving contact support, one end of the connecting rod is connected with the operating handle, and the other end of the connecting rod is connected with the middle position of the moving contact support and is in sliding fit in the sliding groove. And a blocking and limiting structure of the quick closing piece is arranged, so that the closing action of the moving contact support can store energy at first and then release energy to realize quick closing, the closing force is large, the speed is high, and the contact is stable.