On the basis of the decision of a problem on the established flow of a nonlinear viscoelastic fluid with one tensor the internal parameter between parallel planes under the influence of constant pressure gradient finds communication of the flow rate from a pressure gradient at various values of width of the channel. It allows to coordinate at the set expense values of a pressure gradient, components of stress tensor and longitudinal speed in entrance and target sections of the channel at change of its width. Also dependences of components of stress tensor and from a gradient of pressure and distance to a wall are numerically found longitudinal velocity.