Disclosed is a device and method for dynamic extrusion molding of plastic articles having variable micro-channel. The device mainly includes a single-screw extruder, a dynamic extrusion die, a fluid source, a water sink, a tractor, a winding device, and a data acquisition and control system. Near outlet of extrusion die, when the end portion of a syringe needle is at different positions, the inner diameter of the micro-channel of the extrusion molded plastic article is also different. When the hollow syringe core within the dynamic extrusion die performs a high-frequency short-range vibration along an extrusion direction, the inner diameter of the micro-channel of the extruded plastic articles is dynamically variable. The plastic articles of variable micro-channel of the present invention has novel structure with high dimensional accuracy, and a variety of varying patterns, it can be stably produced by simple processing equipment with high level of automation.