The invention relates to a preparation method of a microreactor for experimenting influence of micro-nano particles on cells. The preparation method disclosed by the invention comprises the following steps of (A), sufficiently and uniformly mixing the cells and the micro-nano particles in polyanion isotonic solution to form a mixed solution; (B), dropping the mixed solution in a collecting tank containing divalent cation isotonic solution by using an electrostatic micro-injection machine to obtain a gel microsphere wrapped with the cells and the micro-nano particles; (C), putting the gel microsphere obtained in the step (B) in polycation isotonic solution to form a polycation wrapping film, then, putting the gel microsphere obtained in the step (B) in the polyanion isotonic solution and oscillating to form a polyanion wrapping film, and repeating the operation for 0-3 times to obtain the gel microsphere with 2-8 wrapping films; and (D), putting the gel microsphere obtained in the step (C) in divalent cation isotonic displacement solution so as to obtain the micro-reactor for experimenting influence of the micro-nano particles to the cells. According to the micro-reactor prepared by the invention, the cells and the micro-nano particles are contacted sufficiently; the cells and the micro-nano particles are accurate to measure, and thus, the influence relationship of the micro-nano particles on the cells can be reflected more accurately and reliably.