The possibility of producing blended yam by using one spinneret is analyzed theoretically, especially the formation of differences in linear density and shrinkage between the monofils. Under the same spinning pressure, the die-spinning nozzles with different diameters are used to produce the differences in the flow of the melt. According to the hagen-poseuille equation for streamline flow in cylinder pipe, the volumetric flow rate and the mean melt speed of die-spinning nozzles increase with the increase of diameters. Under the conditions that the winding speeds are the same, so that the effective draw ratios decrease with the increase of the die-spinning nozzles diameters. Then, the filament formed through the die-spinning nozzle with large diameter is coarse and have a low birefringence. On the contrary, the filament formed through the die-spinning nozzle with small diameter is fine and have a high birefringence. The differences between the filament in structure and property could be acquired by one spinneret.