Lab on a chip was mainly used in the simplification of biomedical detection step and separation was one of the indispensable pretreatment during the detection process. In this study, a combination channel of spiral and backward facing step patterns were designed to optimize the separation function without any extra power like electric or magnetic field. The foil-assisted CO2 laser method was used to fabricate a spiral microfluidic chip with polymethylmethacrylate polymer for the master of suspended particles separation. The laser ablation generated poor surfaces quality with bulge and scorches can be diminished using foil-assisted laser micromachining technique. The low-cost and time-saving procedure, including microchip fabrication and surface modification, has been developed to apply positively in microfluidic separation chip based on the flow distribution design of spiral dean vortices and backward facing step, which can provide 99% separation efficiency within a certain flow range.