The invention discloses a cigarette rod diameter detecting and eliminating device. The device comprises a frame; the frame is provided with a first-grade conveying belt and a second-grade conveying belt, which are joined with each other; an input end of the second-grade conveying belt is positioned rightly below an output end of the first-grade conveying belt; a first rolling shaft is arranged atthe output end of the first-grade conveying belt; the distance between the first rolling shaft and the first-grade conveying belt is equal to a qualified cigarette rod diameter; a first pushing and beating device is arranged between the first rolling shaft and the first-grade conveying belt; a second rolling shaft is arranged at an output end of the second-grade conveying belt; a gap between the second rolling shaft and the second-grade conveying belt enables cigarette rods, smaller than the qualified cigarette rod diameter, to fall out; and a second pushing and beating device is arranged between the second rolling shaft and the second-grade conveying belt. The device only can automatically detect if the cigarette rod diameter is qualified, and can eliminate the cigarette rods larger thanor smaller than the qualified cigarette rod diameter to save both time and labors.