The invention relates to a horizontal type dynamic pressure over-speed test device of a commutator. The horizontal type dynamic pressure over-speed test device is characterized by comprising a protective cover, bearings, an output shaft, a lining, a pressing plate, a gland nut, a chassis and a driving mechanism. The two ends of the output shaft are respectively installed in a bearing pedestal through the bearings in a supported mode, the bearing pedestal is fixed on the chassis, a limiting boss is arranged on the output shaft which is meanwhile sleeved with the detachable and replaceable lining, the size of the external diameter of the lining is matched with that of an inner hole of the commutator to be tested, the commutator is arranged on the lining of the output shaft in a sleeved mode, the inner hole of the commutator is in clearance fit with the lining, the commutator and the gland nut are fixed through the pressing plate, the output shaft is driven by the driving mechanism to rotate, the periphery of the commutator is covered by the protective cover, and the protective cover is fixed on the chassis. The horizontal type dynamic pressure over-speed test device is simple in structure, convenient to use, low in manufacturing cost and capable of directly mastering and controlling the quality of the commutator. Materials and parts required by the horizontal type dynamic pressure over-speed test device are all conventional parts, can be conveniently manufactured, and are low in cost.