In this paper, the authors present a new low-level birefringence detection (LLBD) system using photoelastic modulation technology. The LLBD system, operating at wavelength 1152 nm, determines point-by-point the magnitude and orientation (angle of fast axis) of birefringence therefore stress states in the sample. The principle of this LLBD system was described and experimentally verified. The resultant instrument shows high sensitivity and good repeatability for measurement. A sensitivity of magnitude of birefringence about 0.03° (or 0.096 nm at 1152 nm) was established for measurement. Several samples with different levels of birefringence were studied using LLBD system.