The embodiment of the invention discloses a food packaging bag. The food packaging bag comprises a first plastic packaging bag body and a second plastic packaging bag body. The first plastic packagingbag body is arranged inside the second plastic packaging bag body. The opening position of the first plastic packaging bag body and the opening position of the second plastic packaging bag body are arranged in a sealed mode. The outer side face of the first plastic packaging bag body and the inner side face of the second plastic packaging bag body form an enclosed space. The enclosed space is filled with an aqueous solution including an electrolyte, and an insulated heating body is arranged in the aqueous solution. A power-on port is formed in the outer side of the second plastic packaging bag body and is further electrically connected with the insulated heating body through an insulated wire. The enclosed space formed between the first plastic packaging bag body and the second plastic packaging bag body is filled with the aqueous solution, and when food put in is too hot, the aqueous solution can absorb heat. If the food needs to be heated, electrifying only needs to be conducted through the power-on port, the insulated heating body can heat the aqueous solution so that the food can be heated, and functional diversification of the food packaging bag is achieved.