A new method, floating-reference, can efficiently reduce the influence of the physiological background variations on the blood glucose measurement by differentially processing two signals from reference point and measuring point. In this paper, the reference point, where the diffuse reflected light is not sensitive to the variation of glucose concentration, is theoretically proved. Then Monte Carlo simulations are applied to study the radial distribution of the diffuse reflectance at different glucose concentrations for the skin. Moreover, the experiments are constructed to measure the radial distribution of the diffuse reflectance by the intralipid solutions with different glucose concentrations. Both the results from simulation and experiment validate the existence of floating-reference point. By theoretically analyzing the background noises and their disturbing mode on the blood glucose detection, a novel data processing method based on the reference point is proposed to effectively extract the blood glucose information. And it is found from our preliminary experiments with intralipid samples that, this data processing method can reduce the influence of background variation on the extraction of real glucose signal and thus enhance the resolving capability on glucose concentration.