Abstract: Ionospheric anomalies before strong earthquakes have been evidenced by many kinds of observations. Analyses of ionospheric anomalies characteristics and investigation of the corresponding physical mechanism are of great significance to monitoring seismic precursors. China Research Institute of Radiowave Propagation (CRIRP) has conducted a series of studies on the ionospheric anomalies before earthquakes and investigation of the corresponding physical mechanisms based on several decades of ionosonde data recorded by the National Radio Observation Network in China, and preliminarily obtained characteristics of ionospheric anomalies before earthquakes and established a comprehensive model of lithosphere-atmosphere-ionosphere electric coupling. This paper reviews the recent progress of the relevant studies, and gives tendentious emphasis for further study.