The invention discloses a micro-channel continuous reaction synthesis method of an ultraviolet absorber Octocrilene. The ultraviolet absorber Octocrilene is synthesized from benzophenone and 2-ehylhexyl cyanoacetate with an organic solvent as a reaction medium and a sodium methoxide solution or a sodium ethoxide solution as a catalyst through a micro-channel reactor; during preparation, firstly, the benzophenone and 2-ehylhexyl cyanoacetate are uniformly mixed with the organic solvent to obtain a raw material mixed solution; then, the raw material mixed solution and the catalyst are fed as parallel flows into the micro-channel reactor to react at a temperature of 25-100 DEG C and a pressure of 5.0-6.0 MPa with a residence time of 5-15 minutes, and a reaction liquid from an outlet is collected as the crude product of Octocrilene; subsequently, the crude product of Octocrilene is refined to obtain the fine product of Octocrilene with a yield of greater than or equal to 90%. The micro-channel continuous reaction synthesis method of the ultraviolet absorber Octocrilene has the advantages of simple synthesis route, high reaction rate and short production period, and also ease of operation, high yield and low cost, and is prone to industrial production.