The invention discloses a DOAS measurement system by means of polarizing beam splitting. The DOAS measurement system comprises a lambda / 4 wave wafer, a polarizing beam splitting piece, a parabolic mirror primary mirror, a corner mirror, an optical fiber, a power source device and a spectrograph detector. By means of the characteristics of the polarizing beam splitting piece, due to the fact that a signal carrying an absorbing spectrum passes through the lambda / 4 wave wafer for two times, the polarizing state will change, and the signal will be reflected to the receiving optical fiber by the polarizing beam splitting piece; due to the fact that a telescope stray light signal which does not carry the absorbing spectrum and is not in atmospheric transmission does not pass through the lambda / 4 wave wafer, the polarizing state does not change, and the signal passes through the polarizing beam splitting piece and will not be reflected to the receiving optical fiber by the polarizing beam splitting piece. Compared with an existing light-path receiving and transmitting integrated DOAS measurement system, the DOAS measurement system can reduce the proportion of stray light inside a telescope and scattered light in the atmospheric background in the measurement signals, also improve the signal to noise ratio of DOAS measurement on the premise that the lighting effect is ensured, and improve the detection precision of the DOAS.