By the use of the concept of reactance compensation, the integrated series bulk effect oscillator, being compensated to increase the tuning bandwidth is reported. In C-band, the relative bandwidth is greater than 10 percent,the output power is greater than 30 mW, and the change of power is less than 3 dB. The analytical expression of tuning bandwidth and the design of oscillator circuit are given.The combined microstrip with coaxial line structure is adopted for the oscillator. Shunt resonance is changed into serier resonance. The integrated wideband bulk effect oscillator has a wide application in radar and radio communication.