Abstract: The effects of the small tilted inner conductor in a coaxial-gyrotron on the quality factor Q, resonant frequency, electronic interaction efficiency, and Ohmic losses are investigated. A 170 GHz megawatt coaxialgyrotron is analyzed. The results show that the quality factor Q decreases slightly when the tilt angle θ increases.The electronic interaction efficiency drops slightly when θ increases within the range of 0°-0.5°. However, it drops at a faster rate when θ is larger than 0.5° because of mode competition. If θ increases to 1.5°, due to mode competition, the efficiency decreases sharply to only about 4.1%. For both cold and hot cavities, the resonant frequency decreases very small with θ increasing. As regards Ohmic loss density distribution, the tilted inner conductor changes the Ohmic loss density distribution on the inner conductor and makes it form a symmetrical distribution with a tilted axis. Meanwhile, it has little effect on the Ohmic loss density distribution on the outer conductor.