In a continuing effort to develop a noninvasive means of monitoring glucose levels using many methods. In this paper a laser, closed-loop, system was designed and a model was developed to extract the glucose concentration information by Faraday rotation with Terbium Gallium Garnet Crystal(TGG Tb3Ga5O12). The system was tested using various concentrations of glucose. The results show that for a static, non-moving sample, glucose can be predicted. For the physiologic range (0-16mmol/l) for either laser wavelength (523nm or 632.8nm), the Correlation coefficient value (R2) are 09977and 0.9995 respectively. The measurement results of 24 hours show the system with good stability, which error is less than 0.05%.