The invention provides a gas-solid two-phase flow visible combustion furnace with a purging function. The gas-solid two-phase flow visible combustion furnace mainly comprises a furnace chamber and a top cover, wherein the furnace chamber is composed of a long quartz tube and a short quartz tube, and the short quartz tube is inserted from the bottom end of the long quartz tube and is embedded in the long quartz tube. The invention further provides a combustion test device comprising the visible combustion furnace. The combustion test device further comprises a flue gas analyzer, a high-speed video camera, an infrared thermal imager and an XRD/XRF/scanning electron microscope tester which are electrically connected with a main control computer respectively, wherein the high-speed video camera and the infrared thermal imager are arranged in a manner of facing the tube wall of the long quartz tube. The combustion test device can observe the slagging and slag removing process of biomass particle fuel in the combustion process clearly, can record combustion images of the whole combustion process in real time, can record the dynamic process of images and motions that are invisible to thenaked eyes such as combustion flame, turbulence flow and gas-solid two-phase flow of the biomass particle fuel and overall temperature distribution condition of a tested object at high frequency.