A filtering scavenging gasoline brush cutter adds a filter screen in a scavenging path of a two-stroke gasoline engine, thus providing emission reduction and standardizing effect; the filter screen (58) in the scavenging path is arranged close to a technology joint plate (55) or below the scavenging path; the filter screen in the scavenging path comprises a plurality of metal wires braided in longitude and latitude mode, and can filter and regulate breathing between cylinder gas and a crankcase; a plurality of wedges (11b) are arranged to match with the noise control filter screen; the wedges comprise many hollow six-edge shapes; the top of the six-edge shape is provided with a small hole; air flow firstly enters the wedges for compression, then exits the wedge small holes for expansion, thus controlling the noises; a catalyst ree; (59) is arranged and comprises platinum, rhodium, indium and iridium, thus providing catalyst effect for passing gas, and smartly reducing gas noises and HC discharge. A cutter plate (64) with inner sawteeth (642) can prevent cutter relieving; a carburettor of the engine comprises a four-wing nozzle (70a) for atomization; a cutting machine comprises a plurality of outer sawteeth and inner sawteeth, thus preventing the cutter relieving conditions when trimming hard items; the filtering scavenging gasoline brush cutter is low in emission, and a discharge port is far away from people; many measures can improve the quality and usability of the brush cutter.