The source parameters of 85 earthquakes(117.5°～119.5°E,39°～41°N) above M_L 2.5 in Tangshan earthquake area from January 2016 to July 2020 were analyzed by using spectral analysis method. We found that the stress drop of Tangshan Earthquake region is 0.1～10.3MPa,mainly 0.1～1.0MPa,and 81% of the earthquakes with stress drop less than 2MPa. For the earthquakes with magnitude between M_L2.5 and 3.5,there is no obvious relationship between the stress drop and corner frequency and the magnitude. There are few earthquakes with magnitude above M_L4.0,but the stress drop increases with the magnitude increasing,and the corner frequency tends to decrease with the magnitude increasing. In between the M4.5 earthquake in Fengnan district,Hebei on December 5,2019,and the M5.1 earthquake in Tangshan on July 12,2020,there were seven earthquakes of M_L2.5 or greater,ranging in magnitude from M_L2.5 to 2.8. The analysis indicates that there are two obvious high stress drop events before the M5.1 Tangshan earthquake. These two high stress drop events show high value of stress drop and high corner frequency,and the small focal size indicates that more energy is released per unit volume. Both events occurred within 17km distance from the M5.1 Tangshan earthquake,which may be a sign of high tectonic stress in the source region before the 2020 Tangshan M5.1 earthquake.