Abstract: The starting magnitude of b-value spatial scanning is selected to scan and analyze b-value space before medium-strong earthquakes in inland Fujian province. The results show that before most medium-strong earthquakes, there will be b-value spatial scanning anomaly at or near the epicenter, and the b-value anomaly lasts until the onset of most moderate and strong earthquakes, and the duration of the anomaly is related to the number of medium-strong earthquakes within the anomaly range of 1 ~ 2 years. In general, the more medium-strong earthquakes occur in the anomaly range, the longer the duration of the anomaly before the earthquake.