Abstract: Based on the analysis of power spectrum of EEG in 100 normal sub-jects and 52 patients with idiopa-thic epilepcy the present study pro-ved that by using high power spec-truln indexes the positive diagno-sis rate could be raised and the functional states of the brain in epileptics be demonstrated objecti-vely.On 52 epileptics the positive diagnostic rate was 32% by conven-tional visual analysis,whereas it was raised to 56% by using high power spectrum indexes.The extent of the brain damage could be gra-ded according to the bights of spe-ctrum valncs.So this index may be useful in assisting the clinical diagnosis.