Abstract: The measurement on the electron density of NF₃ capacitively coupled by the microwave resonance probe，to get the change rules of NF₃ plasma with the power of electrodes.To measure the density of the NF₃ capacitively coupled plasma by microwave resonace probe through change the power and frequency of top and lower electrode when the pressure is 1 Pa or 5 Pa，so that to get the rule of the electron density of the electronegative NF₃ plasma，and know the influence on the power and frequency of the main power and the minor power.The result shows that，in high electronegativity NF₃ plasma，the increase of the input power and frequency of the minor power sources has little effect on the change of electron density，while the change of input power of main power supply is decisive.