An M4. 8 earthquake occurred in the joint area of Guye and Luanxian of Tangshan city on May 28，2012． The macroscopic epicenter was located in Wangnianzhuang in Guye region． The Intensity of epicenter was Ⅴ degree． The earthquake occurred in the middle of Tangshan Fault in the northeast direction． The earthquake caused no human casualties and economic losses． In the focal mechanism solution，the azimuth of P axis was SEE and T axis was SSW near horizontal． It was not uniform with the tectonic stress field in North China，which is in NE-NEE direction． The M4. 8 earthquake was undulation of the aftershocks of Tangshan M7. 8 earthquake occurred in 1976． The over ML4. 0 earthquakes in Tangshan area showed a quasi-periodic characteristic． There were some background anomalies both in seismicity and seismometry before the event，and they reflected the quiet and undulant process of the seismic activity in the old earthquake region from different views． The precursory anomalies were mainly middle and short term ones，in which groundwater and electromagnetic anomalies were obvious． The magnitude of the earthquake was not high，but it showed many anomalies，both in seismicity or precursor． The anomalies matched very well，in which there were both tendency and current ones．