The invention belongs to the field of particle separation, and discloses a microfluidic device for efficiently separating particles in viscoelastic fluid, which comprises a cover plate layer and a slide glass arranged at the bottom end of the cover plate layer, a blind sidewalk is formed in the end face of the bottom end of the cover plate layer, the blind sidewalk comprises a liquid adding area, a micro-nano particle enrichment channel, a first expansion area and a second expansion area which are sequentially communicated, and a plurality of micro-nano particle collection areas are arranged at the end, away from the first expansion area, of the second expansion area; a structural body is further arranged on the bottom end face of the cover sheet layer, one end of the structural body is located in the first expansion area, the other end is located in the second expansion area, and the surface of the structural body is connected with the surface of the slide glass; a plurality of through holes which are respectively communicated with the liquid adding area and the plurality of micro-nano particle collecting areas are formed in the cover plate layer. The device has the advantages of short channel length, high separation efficiency, no pollution, convenience in operation, simple structure, low cost, convenience in carrying, easiness in integration and the like, and effectively solves the problems of long channel length and low separation efficiency.