A problem in terms of the accuracy of noninvasive measurement of blood glucose with near-infrared (NIR) spectroscopy is mainly caused by the weak glucose signal and strong background variations. We report the existence of the radial reference point in a floating-reference method, which is supposed to solve this problem. Based on the analysis of the infinite diffusion theory, the local condition of the reference point is deduced theoretically. Then the experiments using the intralipid solutions are constructed to testify the existence of the reference point. In order to further validate our results, Monte Carlo simulations are performed to calculate the diffused light distribution according to the variation of the glucose concentration in the intralipid solutions. All the reference points existing in three-layer skin model are also listed at the wavelength of 1200-1700 nm.