The invention discloses a multinational plug adaptor. By the multinational plug adaptor, a product can be effectively thinned, and a structure is simplified. The multinational plug adaptor is provided with a socket body, wherein an opened cover is arranged on the socket body, one side of the opened cover is pivoted with the socket body and is opened or closed around a pivot position, a plug ground pin is arranged at an inner side of the opened cover and slides or rotates at the inner side of the opened cover so as to extend out of the opened cover, and the plug ground pin and a conductive pin extending out of the socket body form a plug with a ground pin. By the multinational plug adaptor, a travel power supply product of a multinational plug is effectively thinned; by arranging the opened cover on the socket body and arranging the plug ground pin in the opened cover and by matching of the plug ground pin and the conductive pin, conversion between a two-pin plug and a three-pin plug is completed, the thinned product can be provided with the plug ground wire used for opening a safety protection cover at a socket hole corresponding to a socket, and thus, the purpose of the product is improved; and moreover, the multinational plug adaptor can be more convenient to carry due to thinning characteristic.