Online particulate matter monitoring device and method based on single light source

The invention provides an online particulate matter monitoring device and method based on a single light source. The device comprises the single light source, a birefringent crystal, a detector and an analysis unit, wherein the single light source emits circular polarized light which penetrates through the birefringent crystal to generate two linearly polarized light beams with polarization directions perpendicular to each other, circular polarized light also penetrates through a detection area, the detector is used for converting particulate matter into electric signals through scattered light signals of the two linearly polarized light beams respectively and sending the electric signals into the analysis unit, and the analysis unit is used for obtaining the size of particulate matter in the detection area according to the received electric signals. The device has the advantages of being high in detection efficiency, low in cost and the like.