The invention belongs to the technical field of drainage of natural gas wells and particularly relates to a slow release type liquid-carrying and sand-carrying foam drainage agent and a preparation method thereof. The slow release type liquid-carrying and sand-carrying foam drainage agent is prepared from sodium fatty alcohol ether sulfate, cocamidopropyl betaine, fatty alcohol-polyoxyethylene ether, octadecyl dihydroxyethyl betaine, hexadecyl trimethyl ammonium bromide, polyvinyl alcohol and a casing in a certain ratio through four steps including adding of sodium fatty alcohol ether sulfateto a stirrer, adding of the remaining components to the stirrer, still standing and curing forming. The slow release type liquid-carrying and sand-carrying foam drainage agent has better salt tolerance and mineralization resistance and has a slow release effect. The foam drainage agent is dissolved slowly and can carry a liquid and sand out of a shaft simultaneously, thereby guaranteeing normal production of a gas well.