The invention provides a gas lift reverse circulation sand washover well washing process and equipment for a sandstone geothermal well. The process comprises the following steps: in a sand washover process, compressing gas in a gas storage tank by an air compressor to form compressed gas; feeding the compressed gas into a gas injection tube from a high-pressure pipeline through a gas feeding tubevia a cavity between an internal body and an external body; then delivering the compressed gas from a gas injection tubular column and a gas mixing tubular column to a gas mixer and mixing the compressed gas with sand washover liquid to generate a gas lift effect; and raising gas, liquid and solid three-phase liquid flow lifted by gas from a sand washover oil tube and then enabling the gas, liquidand solid three-phase liquid flow to enter the internal body of a double-walled gas injector and a water eye of a lower joint so as to reach a ground liquid storage tank via the high-pressure pipeline. The equipment comprises the double-walled gas injector, the gas injection tubular column, the gas mixing tubular column, a sand washover nib and a sand washover drill bit. By a gas lift reverse circulation sand washover technology, a circular suction ability is high, raising of well bottom or water layer settled sand is facilitated, moreover, the sand washover liquid flow can carry large dirtysand particles, repeated breakage of the dirty sand particles is reduced, and therefore, the sand washover efficiency is improved.