The embodiment of the invention provides a gas particulate matter measuring method and device. The gas particulate matter measuring method comprises the following steps: measuring gas particulate matters through a laser radar to obtain radar echo signal strength; determining light extinction coefficients of a molecule and backscattering coefficients of the molecule; inputting the radar echo signal strength, the light extinction coefficients of the molecule and the backscattering coefficients of the molecule into a preset discrete laser radar equation and calculating to obtain particulate matter concentration intermediate parameters; inputting the particulate matter concentration intermediate parameters into a preset polynomial regression equation and calculating to obtain particulate matter concentration. According to the gas particulate matter measuring method and device provided by the embodiment of the invention, as the particulate matter concentration is obtained through the preset discrete laser radar equation and the preset polynomial regression equation, the large range and high precision measurement of the particulate matter concentration can be realized only through the laser radar, and a PM measuring instrument is not required to be used, so that the quantity of used instruments during measurement is reduced, and the cost is reduced.