The invention discloses a method and a device for detecting a charging state, which is used for preventing charging failure because a charging protocol cannot be recognized. The method disclosed by the invention comprises steps of monitoring the real-time current of a USB interface on power supply wire of an inserting end of a terminal device, determining the charging state of the terminal device according to the real-time current, and indicating to anew recognize the charging process of a charger if the charging state shows that the charging is abnormal. The invention can prevent the abnormal charging because of failing to recognize the charging protocol correctly, improves the user experience and completes the charging function of the terminal device.