使用华北地区1972～1992年的中小地震震级资料进行地震强度因子均值空间扫描，研究华北地区中强以上地震前的短期异常变化。结果表明，在震前0．5a左右的短期阶段，Mf值中期异常区存在二类不同形态的变化，其中大部分震例的Mf值中期异常区出现明显的缩小乃至消失，可将这一特征作为短期异常的标志；而另一部分展例的中期异常区无明显变化。文中讨论了Mf值用于短期地震预报的方法和预报效果，并对峙值的短期变化过程进行了定性的物理解释。 The magnitude data of moderate and small earthquakes in North China from 1972 to 1992 were used to scan the mean value of seismic intensity factor to study the short-term anomalies before the strong earthquakes in North China. The results show that in the short-term stage of about 0.5a before the earthquake, there are two different types of Mf mid-term anomalies, of which the Mf anomalies in most of the earthquakes have obviously diminished or even disappeared. As a sign of short-term anomalies; while the other part of the mid-term abnormalities showed no significant change. In this paper, the methods and forecasting results of Mf values ​​for short-term earthquake prediction are discussed, and the qualitative and quantitative interpretation of the short-term variation of the stand-off values ​​is carried out.