The invention relates to a skid-mounted device for ultrasonically dehydrating, removing liquid, purifying and separating for natural gas, belongs to an energy-saving purification device of heat engineering, and is mainly applied in the field of dehydrating, removing liquid, purifying and separating for natural gas. The device consists of a gas purification device and a gas separation device. Wet natural gas enters an ultrasonic separation spray pipe respectively; because the temperature is reduced, water and heavy paraffin hydrocarbon components in the natural gas become liquid and then are condensed to form high-speed rotational flow to tangentially flow into a hydrate separator cylinder; and then three-phase separation of the natural gas, condensate and water is carried out, and simultaneously the hydrate is prevented from being generated. The device efficiently separates out the water and the heavy hydrocarbon liquid from the natural gas without adding any chemical drugs, has the advantages of energy conservation, environmental protection, compact structure, and little occupied area, reduces the running cost, can achieve unmanned operation and free maintenance, and can be applied to remote or severe environmental land and offshore platforms.