The present invention relates to a photoelectrical feedback sensing system. A first light signal passes through the sensing apparatus. A second light signal corresponding to a characteristic of a sample within the sensing apparatus is outputted from the sensing apparatus. The first photo detector receives the first light signal and outputs a first electric signal corresponding to the intensity of the first light signal. The second photo detector outputs a second electric signal corresponding to the intensity of the second light signal. A driving signal is generated by the micro-processor to drive the light-emitting unit. The micro-processor receives the second electric signal and converts the second electric signal into a digital signal. The feedback circuit modulates the driving signal for maintaining the optical stability of the first light signal so that the sensing system is less affected by environmental temperature fluctuation and noise interferences.