A gear shifting system (10, 10', 50) for lowering a motor rotational speed during gear shifting of a pedal-assisted bicycle, arranged on a pedal-assisted bicycle having a mid-mounted motor and a gear shifter, being characterized in that the gear shifting system comprising: a power module; a micro-computer (21, 21', 61) electrically connected to the power module and the mid-mounted motor and used for controlling an outputted assisting force and a rotational speed of the mid-mounted motor; and a vehicle speed sensor module electrically connected to the micro-computer (21, 21', 61) and used for detecting a vehicle speed of the pedal-assisted bicycle; the micro-computer (21, 21', 61) having a motor rotational speed control logic (22, 22', 62, 62') and a vehicle speed/motor rotational speed correspondence table; during gear shifting, the micro-computer (21, 21', 61) executing the motor rotational speed control logic (22, 22',62, 62') the vehicle speed/motor rotational speed correspondence table referring to motor driven rotational speeds for driving the pedal-assisted bicycle at various different vehicle speeds respectively; a process of the micro-computer (21, 21', 61) executing the motor rotational speed control logic (22, 22', 62, 62') characterized by including: finding a motor driven rotational speed corresponding to a current vehicle speed based on the vehicle speed/motor rotational speed correspondence table; controlling the mid-mounted motor to be of a rotational speed lower than the motor driven rotational speed corresponding to the current vehicle speed but still maintaining a rotation of the mid-mounted motor such that a driving force of the mid-mounted motor is not transmitted to the pedal-assisted bicycle in a way similar to an idle rotation, during which the mid-mounted motor provides no driving force; after gear shifting completed, controlling the mid-mounted motor to return back to a motor driven rotational speed prior to gear shifting. a power module; a micro-computer (21, 21', 61) electrically connected to the power module and the mid-mounted motor and used for controlling an outputted assisting force and a rotational speed of the mid-mounted motor; and a vehicle speed sensor module electrically connected to the micro-computer (21, 21', 61) and used for detecting a vehicle speed of the pedal-assisted bicycle; the micro-computer (21, 21', 61) having a motor rotational speed control logic (22, 22', 62, 62') and a vehicle speed/motor rotational speed correspondence table; during gear shifting, the micro-computer (21, 21', 61) executing the motor rotational speed control logic (22, 22',62, 62') the vehicle speed/motor rotational speed correspondence table referring to motor driven rotational speeds for driving the pedal-assisted bicycle at various different vehicle speeds respectively; a process of the micro-computer (21, 21', 61) executing the motor rotational speed control logic (22, 22', 62, 62') characterized by including: finding a motor driven rotational speed corresponding to a current vehicle speed based on the vehicle speed/motor rotational speed correspondence table; controlling the mid-mounted motor to be of a rotational speed lower than the motor driven rotational speed corresponding to the current vehicle speed but still maintaining a rotation of the mid-mounted motor such that a driving force of the mid-mounted motor is not transmitted to the pedal-assisted bicycle in a way similar to an idle rotation, during which the mid-mounted motor provides no driving force; after gear shifting completed, controlling the mid-mounted motor to return back to a motor driven rotational speed prior to gear shifting.