In the textile industry, a cross-lapper is used to produce uniform layers of fibers with suitable widths and thicknesses. In this paper, first, Hamilton's principle is used to formulate a mathematical model of a cross-lapper, then the nonlinear model is linearized to get is corresponding open loop transfer function. Next, the root-locus technique is employed to design the controller for the system. Finally, the designed controller is verified by the original system nonlinear model. The designed controller can have not only very good tracking properties, but can also eliminate the effect of system disturbance.