A tightly closed structure of a glass door comprises a doorframe and a first door panel. An upper containing groove is transversely arranged at the top of the doorframe and a lower containing groove is transversely arranged at the bottom of the doorframe. An upper frame strip and a lower frame strip that protruding from the first door panel are respectively arranged on the upper edge and the lower edge at the direction which the first door panel faces to the doorframe. The upper frame strip is embedded in the upper containing groove and the lower frame strip is embedded in the lower containing groove. When the first door panel and the doorframe are fastened, the upper frame strip and the lower frame strip are fastened into the upper containing groove and the lower containing groove at the same time, so that the upper frame strip and the lower frame strip can be hidden and make the first door panel and the doorframe to be tightly closed.