Disclosed is a bar image detection mechanism. The mechanism is simple in structure and free of a vacuum system. The mechanism comprises a feeding synchronous belt, synchronous wheels, a storage box, bars, a feeding transferring wheel, eccentric wheels, a detection head, a detection position, a discharging transferring wheel, a discharging plate, a dividing plate, a dividing groove, a rotating synchronous belt, a discharging box, a feeding motor and a rotating motor; each transferring wheel is composed of two half wheels, the feeding synchronous belt passes the middles of the transferring wheels, the gap between the two transferring wheels is adjustable, and due to arrangement of the number of clamping grooves in the transferring wheels, the arc line between two clamping grooves can drive the bars to sufficiently rotate on the detection position; due to the depth of the clamping grooves, the bars are clamped and cannot fall off, and the next bars cannot be disturbed; the eccentric wheels are arranged in the transferring wheels, and deviate from the discharging position, and it is ensured that during feeding, the bars are sufficiently clamped in the clamping grooves, and during discharging, the bars are sufficiently separated from the clamping grooves. The dividing plate and the dividing groove are arranged in the discharging box, due to the dividing plate, the bars pass through or enter the dividing groove, and clamping and separation of the bars can be achieved through the eccentric wheels and the transferring wheels.