In order to optimize the mechanism of the cutting feature of horizontal knife in the soil straw mixture, the similitude method was used to research the cutting process and a model rotary knife roller was designed whose proportion was 1∶2 as real roller. In order to find whether there is a manufacturing error of the model,a three dimensional reconstruction experiment was carried out on the model roller with reverse engineering techniques. The model spiral horizontal knife and bend knife were scanned by the FD-Y685 type three coordinate measuring machine with the side surface of the horizontal knife as the datum plane. The point cloud was obtained and filtered by CATIAV 5 software. The point cloud data were processed with Matlab software. On the basis of that, the spiral curve of the horizontal knife was reconstructed reversely. The results indicated that the maximum distance between those measurement points and theirs reverse points was 6.016 mm, and the minimum distance was 0.624 mm, the average distance was 3.243 mm. The maximum relative error rate between measurement points and theirs reverse points was 5.2%, while the minimum relative error rate was 0.6% and the average relative error rate was 3.6%. Reverse reconstruction was an advanced technology with high precision which was able to accurately measure and reconstruct agricultural equipment shape, especially complicated shape.