A refractive fuel concentration detector comprises mainly a light source device and a light-sensing device. The light source device supplies light source incident on the fuel and refracts light source to the light-sensing device such that a plurality of light sensor therein would respectively output a corresponding electrophysical quantity signal based on the light quantity received. Moreover, a circuit means can be used to obtain concentration information of fuel based on the electrophysical quantity signal output by the light sensors and the tag information of those light sensors.