The cutting, threshing-separating and cleaning mechanism are key units of a combine harvester, their structures and design parameters affect performance of combine harvester greatly. Owing to drawbacks of above apparatus of Chinese model rice-wheat combine harvester, a kind of new reciprocating cutter bar with double knife sections, a superposition drive mechanism for cutter bar, double revolutions axial-flow threshing rotor on identical axis, conical type centrifugal fan for grain cleaning and retracing unit with plate tooth for tailing threshing and etc. have been developed. The tests showed that the united application of above new technology successfully reduced grain damage and separation losses in threshing units, improved the cleaning offence in the cleaning shoe, lessened the vibration on cutter bar and increased the cutting efficiency, therefore the whole performance of combine harvester has been improved.