Through systematic analysis on the relationship between the variation of precursor anomalies of underground fluid and moderate strong earthquakes, it is indicated that there are two kinds of short-term precursor anomaly of earthquake, which are turn style and single style, in Northern China. Based on the earthqauke cases, the characteristics of two kinds of precursor anomaly are discussed. It is considered that the approximately synchronous variation for two kinds of anomaly group in the reg ion should be given special attention to.