The invention relates to a method for undergoing a chlorobenzene nitration reaction by using a micro-channel reactor, belonging to the technical field of application of organic synthesis. In the method, nitric acid, sulfuric acid, water and chlorobenzene are taken as initial reaction raw materials, and processes such as mixed acid preparation, mixed acid and chlorobenzene preheating, mixed acid and chlorobenzene reacting and the like are completed in a micro-channel reactor system. In the reaction, nitro-sulfuric mixed acid is taken as a nitrating agent, the effective concentration of sulfuric acid in the mixed acid is 50-90 percent, the molar ratio of the nitric acid to the sulfuric acid in the mixed acid is 1:1-1:10, the molar ratio of the chlorobenzene to the nitric acid is 1:1.0-1:2.0, the reaction temperature is 50-100 DEG C, and the reaction time is 30-120 seconds. The chlorobenzene transformation ratio is up to 97 percent, the selectivity of nitrochlorobenzene serving as a product is over 96.5 percent, and the ratio of ortho-para nitrochlorobenzene is over 0.6. A strengthened mixed micro-channel reactor adopted in the invention is particularly suitable for undergoing a continuous nitration reaction, and has the characteristics of stable temperature control and safe process.