A novel technique for improving measurement sensitivity of optical rotation based on photo-elastic modulation is presented. The probe laser orderly passes through a polarizer, the sample to be measured, a photo-elastic modulator(PEM), and an analyzer to be detected. Using the least optical elements to avoid the measurement error may introduced by the other optical elements in the detection light path; other than a reference light path is brought in the measurement system, and differential balance detection method is employed to obtain the AC and DC signal, the common mode noise of light source is efficiently eliminated, then the AC signal is preamplified, and output by a lock-in amplifier, the measurement sensitivity of optical rotation is enhanced further. For our verification experiment, the results show that the precision is up to 0.4％, and the sensitivity is up to 3.17×10−7 rad . So our scheme realizes more accurate and sensitive measurement of optical rotation than any one reported previously.