In order to analyze the rate of unthreshing and cleaning loss of small combine harvester with double axial cylinder, double axial cylinder was designed. Parameters of this small combine harvester’s structure were analyzed. The experiment showed that the unthreshing rate of small combine harvester with double axial cylinder was nearly 0, rate of cleaning loss reduce by 39% compared with the single axial cylinder. Small combine with double axial cylinder effectively solves the problem of separating and threshing.