With the aim to deal the problems of the impurity cleaning materials and cleaning fan for D2 models of grain combine harvester, the special structure performance of cross-flow fan with double channels and herringbone variable inclined impeller was discussed from a point of view on cleaning system, including design of herringbone variable inclined impeller and the special structure of volute separation and cleaning air duct. The bench test shows that features and regulation of the orifice free jet meet flow distribution requirements of the pre-cleaning and wind screen cleaning. The matching test to the J4 models showed that the statistical average index were as follows: feed rate of 4.81kg/s, cleaning feed rate of 2.65kg/s, cleaning loss rate of 0.17%, grain impurity rate of 0.65%. The rethreshing thrower works properly.