This application provides a two-speed transmission system. The two-speed transmission system includes a first fixed gear fastened on a first shaft, a first floating gear connected to a second shaft through rotation, a first connection mechanism, and a one-way clutch. The first connection mechanism is configured to implement connection or disconnection between the first floating gear and the second shaft. The one-way clutch is located between the first floating gear and the first connection mechanism. An inner surface of the one-way clutch is connected to the first floating gear. An outer surface of the one-way clutch abuts against the first connection mechanism. The outer surface of the one-way clutch is connected to the first connection mechanism. An acting force of the outer surface directly acts on the first connection mechanism instead of a tooth surface of the first floating gear, to reduce an impact on accuracy of gear transmission.