Abstract: Abstract: There are 2 kinds of methods for oilseed processing, which are mechanical pressing and solvent extraction. In mechanical pressing, screw pressing is widely used in industry for large-scale oilseeds with a low residual oil in cake while hydraulic pressing is suitable for special oilseeds under a low temperature. One-dimensional pressing is the foundation of mechanical pressing especially for new type of oilseeds with high oil content and high protein content. In process of one-dimensional pressing, oilseeds are squeezed and ruptured under the interaction with the barrel by the axial compression and lateral limit. Oils in the cells are gradually squeezed out only leaving the cake inside the cylinder barrel. In order to quantitate the flow state of oil in cold processing by cylinder pressing, experiments for stress analysis of oilseed were carried out on the basis of one-dimensional pressing model, which was established through simplifying assumptions. Based on the Darcy percolation law and the Terzaghi consolidation theory, 4 assumptions were raised: material layer of oilseeds was saturated by oil; gravity of the oil was ignored and oil flowed only in radial direction in cake pores; material of solid particles could be compressed while its volume and true density would not change, and the oil inside the pores could be incompressible; oilseeds remained in the state of saturation when squeezed and the flow of oil obeyed the Darcy seepage law. The influencing factors, including inner diameter, height of material layer, pressing pressure, pressing time, viscosity of oil, and porosity of oilseeds, were determined to establish the percolation model. Cylinder radius was one of the important factors for hydraulic pressing. The oil yield efficiencies were almost invariant with the increase of cylinder radius at first, and then decreased because oils inside pores could not flow out in time. Meanwhile pressure of hydraulic pressing would decrease with the increase of cylinder radius, leading to a difficulty for oil flow. Results of testing experiments of oil yield efficiency under different barrel diameters showed that the maximum error of the model was 2.10%, reflecting a relatively high accuracy of prediction. In practical pressing, the pressing pressure and time could be easily controlled, and the oils' viscosity and the cake porosity could be changed by setting the pressing parameters, while the size of the cylinder was not easy to be changed once chosen, leading to the importance of cylinder radius. Based on the model for oil yield efficiency deduced in this paper, the analysis results of the relationship between oil yield efficiency and cylinder radius show that radius of cylinder should not be too large.