The invention provides a multi-path fiber core test device and method. The device comprises a pulse generator, a light source, a light path switch, a directional coupler, a photoelectric detector, a signal processing device, an MCU (micro control unit) chip and a main clock, wherein the light path switch is provided with a plurality of light transmission ports, each light transmission port is connected with a standby optical fiber, the pulse generator generates electric pulse signals and sends the electric pulse signals to the light source, the light source converts the electric pulse signals into light pulse signals, the light pulse signals are sent to the light path switch through the directional coupler, the light path switch is connected with the standby optical fiber of the corresponding light transmission port, the light pulse signals are transmitted to the standby optical fiber, the fed back light signals are received and are transmitted to the photoelectric detector through the directional coupler, the photoelectric detector converts light signals into electric signals and outputs the electric signals to the signal processing device, the signal processing device generates an illumination intensity-distance performance curve according to the electric signals, and transmits the illumination intensity-distance performance curve to the MCU chip, and the MCU chip compares the performance parameters of the standby optical fibers according to the performance curve and generates a test result.