Measurements of glucose concentration are important parts of biochemical analyses. Based on the principles of the common-path heterodyne interferometry, we develop a high sensitivity optical sensor for measuring glucose concentration. A heterodyne light beam after transmitted through a glucose solution passes through some polarization components for interference. The phase difference determined with heterodyne interferometric technique of the interference signal is greatly enhanced as a result of proper azimuth angles of some polarization components, and a high sensitivity measurement of glucose concentration can be achieved. The feasibility of the measuring method was demonstrated by our experimental results. This optical sensor should bear the merits of high accuracy, short sample medium length, and simpler operational endeavor.