The operating efficiency of cotton picker is mainly related to the parameters such as the drum speed of cotton picking head, number of seat pipes and spindle picking speed and speed ratio between drum and spindle is fixed. Horizontal spindle is the core working part of spindle-type cotton picker, and cotton picking is realized by winding cotton wadding at high speed. The spindle picking speed is key factor affecting effect of cotton picking. The spindle picking speed was theoretically analyzed from three aspects which were picking cotton smoothly, winding up a single cotton petal, and the loss of cotton seed throwing away. According to known picking parameters and mechanical properties of cotton, the speed range of picking spindle was estimated to be 3000～400r/min. In order to verify the range of spindle picking speed obtained by theoretical analysis, a single spindle picking laboratory test device was set up. The single factor test of spindle picking speed was carried out with the indexes of single cotton picking rate, picking time, power consumption and cottonseed rejection rate, which were divided into 1000r/min,2000r/min, 3000r/min, 4000r/min, 5000r/min and 6000r/min test levels. According to the test results, a multi-index optimization mathematical model was established. Under the conditions of approaching seed cotton speed of 0.2m/s, cotton seed rejection rate (no more than 2.5%) and cotton seed recovery rate (greater than or equal to 90%), the range of spindle picking speed was 3600～3700r/min, which was consistent with the theoretical analysis and met the requirement of picking summary.