The invention provides a preparation method for a nano-TiO2 modified micro-channel reactor. The preparation method comprises the following steps: preparing a micro-channel reactor made of a transparent material, and cleaning the micro-channel reactor for later use; adding a
titanium source in an acidic water solution or
ammonia water to obtain a mixture, and stirring the mixture to form nano-TiO2
sol; injecting the nano-TiO2
sol in a channel of the later-use micro-channel reactor, staying for 5-30 min, and injecting deionized water in the channel of the micro-channel reactor for cleaning to obtain a nano-TiO2
sol particle modified micro-channel reactor; placing the nano-TiO2 sol particle modified micro-channel reactor in a 500-1,000 W
infrared source to be illuminated, ultrasonically cleaning the passage with an acidic cleaning solution and deionized water in sequence, and obtaining the nano-TiO2 modified micro-channel reactor. The preparation method has the characteristics of being simple in preparation process, and easy to achieve industrial production; the micro-channel reactor, prepared according to the preparation method, has the characteristics of being high in density, convenient and high in efficiency.