By tracing down anomalies of seismological parameters before Shidian M_S5 earthquake swarm occurred in 2001, the evolution process of preparation and occurrence of moderate earthquakes for mid short and short imminent terms are studied. The result shows:on the background of anomalies of seismicity parameters including b-value, regulatory ratio of small earthquakes and wave velocity ratio as well as the regular migration of moderate earthquakes for middle term in Yunnan province,some mid short term anomalies such as frequency, b-value and strain acceleration in seismogenic zone of western Yunnan appear.Mainwhile some short imminent term anomalies such as continuous frequency increase of earthquakes with M_L ≥ 3.0 and M_L ≥ 4.0, anomaly of daily frequency of earthquakes with M_L ≥ 3.0 and notable quiescence of earthquakes with M_L ≥ 3.0 and M_L ≥ 4.0 also appear in Yunnan province. Especially the anomaly quiescence of earthquakes with M_L ≥ 3.0 and M_L ≥ 4.0 gives obvious mark of imminent information. A preliminary discussion on how to distinguish a single earthquake during the continuous occurrence of moderate earthquakes is made.