The invention provides an open keeping device used for a trunk lid of a car. The open keeping device comprises a hinge base, movable hinge arms, hinge shafts, linings, sleeves and a limiting device, wherein the hinge base is installed on a back partition plate of a back car body of the car; one end of each movable hinge arm is hinged to the hinge base, and the other end of each movable hinge arm is connected to the trunk lid of the car; the hinge shafts are fixedly connected to the two side walls of the hinge base; each lining is fixedly arranged on the corresponding hinge shaft; each sleeve is installed on the outer side of the corresponding lining in a sliding mode; each movable hinge arm is fixedly connected with the corresponding sleeve; each sleeve rotates relative to the corresponding lining along with rotation of the corresponding movable hinge arm; the limiting device is arranged inside the hinge base; the limiting device is in friction fit and shape fit with the outer surfaces of the sleeves so that the trunk lid can be kept in an open position.