Type 9HS-170 yellow corn forage harvester was designed and the overall structure and working principle of the machine was elaborated. The roller device and toss blower which were the core components of machine was analyzed. Trajectory of any point in circular arc section of work of moving blade was trochoidal, through the analysis of the theory of roller device. According to the mechanical properties of corn stalk, the corn stalk could be cut off to be suitable for livestock to chew in cases with fixed blade to cooperate and linear velocity of moving blade of 38.6 m/s. Moreover, peripheral speed of blade terminal was 35.7～42.8 m/s and there was secondary flow in toss tube, through numerical simulation and analysis of the air flow field of toss device by using the software of Fluent. Overall, the design of toss device was reasonable. The field experiment was conducted. The results showed that safety performance and operation performance of type 9HS-170 yellow corn forage harvester were good. The average productivity of machine was 0.7 hm2/h. The average loss rate was 2.8%. The stubble height was 87 mm. The bearing temperature rise was 7℃.