The invention relates to a foaming agent developed for foam drainage of a gas well, in particular to a fatty acid amide propyl betaine foam scrubbing agent as well as a preparation method and an application thereof. The fatty acid amide propyl betaine foam scrubbing agent is adaptable to the highly-mineralized and high-oil-bearing extreme environment with the mineralization degree higher than 25*10<4> mg/L and the content of condensate oil higher than 30%. According to the technical scheme, lauric acid, coconut fatty acid, oleic acid (cis-9-octadecenoic acid) and other fatty acids are added to a reactor in a certain mole ratio and have a condensation reaction with N,N-dimethyl-1,3-propane diamine at the temperature of 140-160 DEG C for 3-4 h, and an intermediate product, namely, long-chain alkyl tertiary amine, is obtained; the intermediate product and sodium chloroacetate have a nucleophilic substitution reaction at the temperature of 60-90 DEG C for 3-6 h, the content of free amine is tested to be smaller than 0.5%, fatty acid amide propyl betaine is obtained after the reaction, and fatty acid amide propyl betaine is a main agent of the foam scrubbing agent for the gas well. The prepared foam scrubbing agent has good foaming and foam stabilizing performance, foams carry a large quantity of liquids, and the foam scrubbing agent has excellent foam flooding performance in various extreme environments and has wide prospect.