Based on microearthquakes fine relocations and focal mechanisms, the paper analyses the causes of clustered microseismicity in Puyang, Henan. The relocated results given by hypoDD shows that the hypocenters of most microearthquakes are situated at the trunk fault of Liaocheng- Lankao fault zone, and its distributions accord with the fault＇s attitude. Focal mechanisms of 5 events with ML l≥ 3.5 show that observed waveforms can be well explained by the double couple model. There are mainly strike-slip mechanisms in smaller events, with quadrantal polarities. On the basis of relative materials on geology and tectonic backgrounds of oilfield, the paper discusses inductive relationship between fluid injection for oil-production and microseismicity in this area.