The invention provides a fast and stable dip angle adjusting tool and method suitable for the whole-satellite AIT overall process. A flat placing plate is provided with a satellite body connection port; kidney-shaped holes are formed in four corners of the flat placing plate; longitudinal screws are arranged in the kidney-shaped holes in a penetrating mode and are respectively provided with two stable wedge blocks in a sleeved mode; the two stable wedge blocks of each longitudinal screw are located on the front surface and the back surface of the flat placing plate respectively and are connected to the flat placing plate in a fastened mode; and the longitudinal screws are respectively provided with two locating nuts in a sleeved mode for locking the stable wedge blocks and the flat placing plate. According to the fast and stable dip angle adjusting tool and method, the structure mode is simple, small-angle adjustment of the whole-satellite posture can be realized easily, conveniently and fast, posture adjustment in the whole-satellite state can be completed fast and effectively, the safety factor of the whole posture adjustment process is high, the manufacturing cost of a turning tool is effectively saved, the adjustment efficiency of the whole-satellite small-angle posture is improved, and the satellite assembly development time is saved to a certain degree.