分析日本 4次地震前 5个电离层垂测站资料 ,发现地震前后震中附近夜间电离层偶发 E层的临界频率 f0 ES值多数呈下降趋势 ,少数呈增加趋势。分析国际地球物理年 ( IGY)期间多个地震震中附近电离层垂测站资料 ,得出 f0 F2 参数变异的统计特性是震前有正扰趋势。本文对震源电场影响电离层的机制进行了探讨。研究表明 ,地震前的电离层异常有可能作为地震前兆 By analyzing the data of the five vertical ionospheric stations before the 4 earthquakes in Japan, it is found that the critical frequency f0 ES values ​​of the sporadic E layer near the epicenter before and after the epicenter show a downward trend and a few tend to increase. Based on the data of ionospheric vertical stations near the epicenter during the International Geophysical Year (IGY), the statistical characteristics of f0 F2 parameter variation are found to be positive disturbance before the earthquake. In this paper, the mechanism of the impact of the source electric field on the ionosphere is discussed. Research shows that the anomalous ionosphere before the earthquake may be used as a precursor of the earthquake