A rope assembly of window blinds includes multiple ropes which are respectively located at front side of the slats and at rear side of the slats of the window blinds. The ropes are connected to a control unit received in the top box of the window blinds. Each rope is received in a sleeve, and at least one support wire is connected between the sleeves located on the front and rear sides of the slats which are supported on the at least one support wire. The at least one support wire controlled by the control unit to lift or lower the slats. The ropes are protected by the sleeves and the sleeves provide aesthetic features.