A coupling process for producing biodiesel from a waste FOG comprising: a step S1 of preheating and dissolving a waste FOG, charging the dissolved waste FOG into a filter to remove solid impurities, and charging the filtrate and a certain amount of a short-chain alcohol and a liquid acid catalyst into a pre-esterification reactor for a pre-esterification reaction to generate a pre-esterified mixture; a step S2 of charging the pre-esterified mixture into a liquid-liquid separator for liquid-liquid separation to separate out an aqueous phase and an organic phase, separating the organic phase using a second flash separator to obtain a pre-esterification product I and an alcohol solvent, and charging the pre-esterification product I into a water scrubber to remove metal ions to obtain an esterification product II; a step S3 of pre-hydrogenating the esterification product II, an oil-soluble hydrogenation catalyst, a vulcanizator, and hydrogen gas in a suspended-bed reactor to generate a product I; a step S4 of charging the product I into a gas-liquid-solid separator, and passing the separated components through a desulfurization adsorption tower and a first pressure swing adsorption tower for recycling and collection of the hydrogen gas and the hydrogenation catalyst, to obtain an oil phase product I; a step S5 of mixing the oil phase product I and hydrogen gas, charging the mixture into a fixed-bed reactor for a deep deoxygenation reaction to obtain a mixed product I, and separating the mixed product I using a first gas-liquid separator to obtain an oil phase product II; a step S6 of mixing the oil phase product II and hydrogen gas, and charging the mixture into a hydroisomerization reactor for an isomerization reaction under an action of a catalyst, to generate a product II; and a step S7 of charging the product II into a second gas-liquid separator to separate out a gas phase and a liquid phase, and charging the liquid phase product into a fractionation tower to separate out isomerized biodiesel and an aviation fuel product. a step S1 of preheating and dissolving a waste FOG, charging the dissolved waste FOG into a filter to remove solid impurities, and charging the filtrate and a certain amount of a short-chain alcohol and a liquid acid catalyst into a pre-esterification reactor for a pre-esterification reaction to generate a pre-esterified mixture; a step S2 of charging the pre-esterified mixture into a liquid-liquid separator for liquid-liquid separation to separate out an aqueous phase and an organic phase, separating the organic phase using a second flash separator to obtain a pre-esterification product I and an alcohol solvent, and charging the pre-esterification product I into a water scrubber to remove metal ions to obtain an esterification product II; a step S3 of pre-hydrogenating the esterification product II, an oil-soluble hydrogenation catalyst, a vulcanizator, and hydrogen gas in a suspended-bed reactor to generate a product I; a step S4 of charging the product I into a gas-liquid-solid separator, and passing the separated components through a desulfurization adsorption tower and a first pressure swing adsorption tower for recycling and collection of the hydrogen gas and the hydrogenation catalyst, to obtain an oil phase product I; a step S5 of mixing the oil phase product I and hydrogen gas, charging the mixture into a fixed-bed reactor for a deep deoxygenation reaction to obtain a mixed product I, and separating the mixed product I using a first gas-liquid separator to obtain an oil phase product II; a step S6 of mixing the oil phase product II and hydrogen gas, and charging the mixture into a hydroisomerization reactor for an isomerization reaction under an action of a catalyst, to generate a product II; and a step S7 of charging the product II into a second gas-liquid separator to separate out a gas phase and a liquid phase, and charging the liquid phase product into a fractionation tower to separate out isomerized biodiesel and an aviation fuel product.