Abstract: This paper systematically analyzed the data of earthquake cases in Beijing and its adjacent area accumulated for many years, and point out that fluid anomaly can be divided by medium-term anomaly, medium-short term anomaly, short-term anomaly and short-imminent anomaly. Using “identity” idea and anomaly criterion of slave function, remain-curve and original-curve deviation etc, a set of medium-term, short-term and imminent-term anomaly of the moderately strong earthquakes, especially those with intensity ≥Ⅴ, above magnitude 5 earthquakes are extracted. Through statistics and analysis of fluid anomaly characteristics, this paper obtained the time distribution characteristics of fluid anomaly of the moderately strong earthquakes, especially those with intensity ≥Ⅴ, earthquakes in Beijing and its adjacent area, and summarized the leading time of each phases anomaly before the earthquakes, which can be regarded as index of occurrence time of earthquakes. It can provide reference for earthquake monitoring in this area.

Key words: Fluid anomaly, Identity, Moderately strong earthquake, Beijing and its adjacent area