Abstract: In reference1, a systematic study of b-value scanning on the seis-mological data of over 10 years obtained in East and West China has been carried out, and the fuzzy evaluation on the predictive effectiveness is studied. In conducting fuzzy evaluation, the average closeness of predicted magnitude, time and piece are 0.34, 0.17 and 0.18 respectively.The average clearness are 0.68, 0.71 and 0.29 respectively.#br#The analysis showes that time and space scanning method of b-value is possessed of a certain predictive capability about the three elements of an earthquake, and can be as one of methodologies for medium term prediction, of couse, the predictive ability of this method today is still,limited.