Abstract: In order to accurately obtain the optimal installed position of the PVDF（polyvinylidene fluoride）entrainment loss sensor, the vertical and horizontal distribution of mixed material under the longitudinal-axial drum were studied with the feed rate of 6, 7 and 8 kg/s. The location installed was selected under the condition that the mass percentage of grain was most stably and the changed mass percentage of other materials was minimum with different feed rate. When the mixed materials were falling under the longitudinal-axial drum, the falling speed changed at the different location. The voltage was studied, which was produced by impact strength of the grain and other materials with different speed. It was turned out that the optimal installed position of the PVDF entrainment loss sensor was the point where i was 6 on the X axial, j was 12 on the Y axial and k was 14 on the Z axial. The differences was 4.50%～5.26% between the record number of values by PVDF entrainment loss sensor and high-speed camera. The studies provide a basis for the installed location of entrainment loss sensor under the longitudinal-axial drum of tangential-longitudinal-axial combine harvester.