In RF wireless communication systems, oscillator plays the role of providing signals, therefore high stability and low phase noise oscillator is very important. This paper use the negative resistance theory of FET, let the circuit is in an unstable state. And the use of dielectric resonator (DR) as a signal source, design of the dielectric resonator oscillator (DRO) operating frequency is 10.5GHz. Use dielectric resonator (DR) of stable frequency characteristics, high Q value characteristics, make the oscillator with a small, low phase noise and other advantages. The design process using the software Agilent's ADS for optimization and analysis results. Final, the output impedance is - 50.15+j0.604, meet the negative resistance circuit design, and output power is 7.95 dBm.