Fedrated learning method using synonym

A federated learning method using synonym includes: sending a general model to every client device by a moderator; performing a training procedure by each client device, wherein the training procedure includes: encoding private data into a digest; training a client model according to the private data, the digest and the general model, and sending the digest and a client parameter of the client model to the moderator; determining an absent client device of the plurality of client devices by the moderator; generating a synonym of the digest corresponding to the absent client device by a synonym generator; training a replacement model according to the synonym and the digest corresponding to the absent client device by the moderator; and performing an aggregation to generate an updated parameter to update the general model by the moderator according to a replacement parameter of the replacement model and the client parameter of every client devices except the absent client device.