Abstract: An operating method of a ketogenic dietary evaluation system includes steps as follows. The electroencephalogram data of a responder group and the electroencephalogram data of a non-responder group are preloaded, in which each electroencephalogram datum includes electroencephalograms of channels. The electroencephalograms of the channels are preprocessed to obtain the preprocessed electroencephalograms of the channels. A connectivity matrix is obtained on a basis of the phase synchronization between each two of the preprocessed electroencephalograms of the channels. The connectivity matrix is sampled and analyzed through different frequency bands and different proportion threshold values to obtain graphical parameters. A predictive model is established on a basis of a reduction rate of a predetermined event of the responder group, a reduction rate of the predetermined event of the non-responder group and the parameters.