Abstract: A new oscillator structure for Gunn chip mounting in integ rated finline is suggested and analyzed with the conservation of complex power technique in this paper. An optimum size of the mounting structure is searched for the best match between the Gunn chip and circuit. Beacuse the structure suggested in this paper is very easy to mount Gunn chip and to tune its resonating freguency, this oscillator has high reliability and wide bandwidth with flat output power. Using this method, a Ka band integrated finiline Gunn oscillator is made with bandwidth of over 12 GHz and mo re than 30 mW out-put power.