Abstract: A bicycle mounting mechanism and battery box assembly installed in a bicycle frame of a bicycle is provided to include a battery box and a mounting mechanism. The battery box includes an abutment recess and an opening. The mounting mechanism includes a grip and a locating component unit being connected to the bicycle frame and defining therein an accommodation chamber for accommodating the battery box. The grip is pivotally connected to the locating component unit and includes an abutment end portion and a push end portion. The abutment end portion is capable of inserting into the accommodation chamber and in engagement with the opening with a rotating of the grip. The push end portion is capable of inserting into the accommodation chamber and abuts against the abutment recess with a further rotating of the grip.