The invention provides a battery replacement system and a battery replacement method for an electric bus. The battery replacement system comprises a battery transport portion, a traveling device and a battery mounting portion. The battery transport portion is provided with a plurality of battery mounting position for battery placement. The traveling device comprises a frame, a connection portion and a driving device, the driving device drives the connection portion to move in a range of the frame, the battery transport portion is pivotally connected with the connection portion, and a pivot shaft of the battery transport portion and the connection is arranged vertically. The battery mounting portion is connected with the battery transport portion and used for driving batteries at the battery mounting positions, and the battery mounting portion comprises a first state in which the batteries are positioned at the battery mounting positions and a second state in which the batteries are pushed out of the battery mounting positions. By the battery replacement system, manual battery replacement is replaced, burdens of workers are relieved, and the problem of low battery replacement efficiency is solved.