The invention discloses an image collecting device and collecting method capable of collecting incident light, scattered light and transmission light information about dust concentration. The image collecting device comprises a light emitter, a light splitter and a light collector, wherein the light splitter splits probe light emitted from the light emitter into transmission light and reflected light, the light collector collects the reflected light and the transmission light penetrating through dust and comprises an optical fiber branch circuit, an optical fiber main circuit, an optical fiber coupler, a collection lens and a CCD camera, the optical fiber branch circuit is arranged at an exit port of the reflected light, the optical fiber main circuit is arranged at an exit port of the transmission light, light outlets of the optical fiber branch circuit and the optical fiber main circuit are connected to an inlet of the optical fiber coupler, and the collecting lens and the CCD camera are connected to an outlet of the optical fiber coupler sequentially. According to the device, the design complexity of the incident light, scattered light and transmission light collecting device is simplified, besides, the measurement accuracy of the incident light, scattered light and transmission light information is improved, and measurement signals can be collected in real time on line.