Machine learning system and machine learning method

A machine learning system includes a host device and several client devices. The client devices receive a host model from the host device, respectively, and include a first and a second client devices. The first and the second client devices store a first and a second parameter sets, respectively, and perform training on the received host models according to the first and the second parameter sets, respectively, to respectively generate a first and a second training results. If the host device has received the first training result corresponding to an m-th training round but has not received the second training result corresponding to a n-th round training, when a difference between m and n is not higher than a threshold value, the host device updates the host model according to the first training result without using the second training result.