The characteristics of the medium-term seismic quiescence before 14 moderate or strong earthquakes in Eastern China are studied.The normalized N-T and L-T curves and the statistical parameter β_n are adopted.Each point in the isopleth map of β_n can show the level of seismic activity and its corresponding duration and end date,which can be utilized to determine the time span of the medium-term quiescence quantitatively.The several seismic activity patterns, with general feature of seismic activity rate from increasing to decreasing before the main-shocks and fluctuation variation of irregular sine wave in N-T and L-T curves,appeared before moderate and strong earthquakes are also summarized.