Abstract: A picking device was designed for mini self-propelled cotton harvester with multi-finger. It was composed of ten groups of chains which were installed with tooth pieces and distributed according to certain roles, and the picking device was unidirectional rotated by driving the sprocket-chain system. The single factor experiment and multi-factor orthogonal experiment were conducted to investigate the influence of the length of tooth piece, tooth piece arrangement on the chain, the rotary speed of toothed chain and forward speed of the picking device on the picking rate, impurity rate and loss rate of the picking device. The results showed that when the tooth pieces were symmetrically mounted on the chain with equal intervals, the length of tooth piece was 22 mm, the rotary speed of toothed chain was 100 r/min and the forward speed of the picking device was 0.3 m/s, the picking rate was 89.74%, which was the maximum, and the impurity rate and loss rate were 10.32%, 6.24%, respectively, which were the minimum.