In order to overcome the shortcomings of the traditional feeding method, the feeding industry of ruminant gradually adopts the ration feeding technology that mixes the nutrient formula of roughage, concentrate and various additives uniformly. The models of foreign ration mixers tend to serialization and automation, but there are disadvantages such as high price, large power, and strong technical confidentiality, which limit the popularization and application of foreign ration mixers in China. Considering the shortage of mechanism study and innovative research of ration mixers, and the actual needs of animal husbandry in China, for promoting the application of ration feeding technology in China, a rotary ration mixer was designed. In order to reveal the mixing mechanism, the rotary ration mixing experimental device was designed and used to observe and analyze the mixing process by the highspeed photography technology. According to the movement characteristics of material particle group in the drum, the material distribution area was divided into material lifting area, dropping area and material returning area. The dropping area was the main mixing area, in which materials were mixed by main shear mixing and auxiliary spread mixing and auxiliary convective mixing. The location, size and shape of each area were affected by the structural and operating parameters. At the same time, the experimental ration was chosen according to the forage-concentrate ratio of 35∶65 (based on dry matter content). Rotary speed of the drum, loading rate of materials, mixing time, inclination angle of the shoveling plate and height of the shoveling plate were used as experimental factors, coefficient of variation and net power consumption were used as evaluation indexes, the method of orthogonal rotational combination experiment of five factors and five levels was used to carry out the optimization experiment of performance. The experimental results showed that coefficient of variation was 2.09% and net power consumption was 33.734kJ under the conditions that rotary speed of the drum was 23.5r/min, loading rate of materials was 65%, mixing time was 4min, inclination angle of the shoveling plate was 11°, and height of the shoveling plate was 109mm. The results could provide reference for the research and development of ration mixers.