Grass trimmer driven by LPG engine

The invention discloses a grass trimmer driven by an LPG (Liquefied Petroleum Gas) engine. The grass trimmer is characterized in that a low-emission gasoline engine combined with double auxiliary ventilation openings of left and right improved narrowing box bases, tapered-wedge turbulence channeling sheets at scavenging air duct openings and double auxiliary piston skirts is adopted, the carburetor of the grass trimmer is provided with a four-fork nozzle (70a) which is beneficial to be atomized; the grass trimmer is unexpected in emission-reducing and standard-reaching effect; a cutter includes a grass trimming head (54) with a cutting and grass-trimming steel wire (54b) and a steel wire nylon string both which are beneficial to cut for a long term, and the cutter is provided with an external protecting cover (73) arranged on an internal protecting cover (60) and a long-time grass pressing wheel (74) arranged on the external protecting cover, and the roller length of the long-time grass pressing wheel (74) is equal to the grass trimming diameter, thus the cutter is convenient to press grasses, preserve soil moisture and decorate grasslands. Propane in a micro propane fuel tank reaches 99% and has few impurities. The micro propane fuel tank is made of a high-pressure extrusion die. The grass trimmer is safe, environmentally friendly, easy to exchange and universally applied to multiple countries, thus the grass trimmer is very popular for international markets.