NOVELTY - A device for preparing natural gas for vehicles by using kitchen waste, comprises a kitchen waste pretreatment device, a uniform pulp heating device, an anaerobic digestion tank, a marsh gas storage cabinet, a desulfurization device and a variable pressure adsorption device which are sequentially connected.    USE - The device is useful for preparing natural gas for vehicles by using kitchen waste (claimed).    ADVANTAGE - The device has the advantages that the kitchen waste can be treated by the device and a method, so that the waste is reused; secondary pollution and toxicity are avoided in the treatment process; the waste treatment method is high in economical efficiency, changes the waste into valuable, and is beneficial to environmental protection. The method is simple, easy to master and convenient to operate. The device is low in investment cost, high in conversion efficiency and easy to popularize and apply.    DETAILED DESCRIPTION - A device for preparing natural gas for vehicles by using kitchen waste, comprises a kitchen waste pretreatment device, a uniform pulp heating device, an anaerobic digestion tank, a marsh gas storage cabinet, a desulfurization device and a variable pressure adsorption device which are sequentially connected, the pretreatment device comprises an upper part which is connected to a bracket of a box body, the top of the box body is provided with a material inlet, the bottom of the box body is provided with a slurry outlet, the box body is horizontally penetrated with a main shaft protecting tray for crusher, where the main shaft protecting tray for crusher are arranged on the outer surface of the crushing cutter head, crushing cutter head are uniformly distributed the outer surface of the main shaft are staggered is provided with an air inlet, an air inlet with the fan connected with the upper part on one side of the box body of the main shaft of the air outlet direction of the fan facing to the box body, the upper part is opposite to the side wall of the box body is provided with a light matter outlet, light matter outlet and opposite to the air inlet, the box body is provided with a connecting main shaft protecting tray for crusher of a driving motor I, the slurry homogenizing heating device comprises a horizontal cylindrical tank body, a tank body cavity is penetrated with a spiral blade of the main shaft, the length of the tank body of the spiral blade, the main shaft is connected with a driving motor II, the upper part of one end is provided with a feeding port, a slurry outlet of the feeding port is connected with the kitchen garbage pre-treatment device is connected, the other end of the lower part is provided with a discharging port, the tank body is covered with a steam jacket; crushing cutter head is connected to the main shaft protecting tray for crusher through the movable pin shaft, some crushing cutter head with each other. An INDEPENDENT CLAIM is a method of preparing natural gas using the device for preparing natural gas for vehicles, comprising: (1) pre-treatment of the kitchen waste: collecting, sorting and removing bone residual material by the magnetic force sorting removing metal foreign matter; (2) placing the raw material obtained in the step (1) into the garbage pre-processing device comprising a driving motor I, driving main shaft and protecting tray for crusher, the step (1) to obtain the raw material, crushing pulping, obtaining waste slurry, process stirring the raw material, at the same time removing the light material; (3) mixing the waste slurry and heating to 30-36 degrees C, adjusting the pH value 6.8-7.2, adjusting the waste slurry with water, making the solid content in the slurry to 10-12%; (4) in the step (3) of preparing slurry for anaerobic digestion treatment, the anaerobic digestion temperature is 35 plus minus 1 degrees C, anaerobic digestion time is 15-18 days; (5) an anaerobic digestion to produce marsh gas enters gas cabinet, then marsh gas is has a pressure of 1.5-2.0 kpa to enter into dry tower desulfurization; (6) the desulfurization of marsh gas to 0.6-0.8 MPa, then removing carbon dioxide (CO2) and water to obtain a purified gas, purified gas to 20-25 MPa, enters the high pressure gas tank storage to obtain the natural gas used in vehicle.