With the aim to analyze pollutant in water, an effective photocatalytic microreactor has been presented in this paper. The microreactor was made of soda-lime glass, and square wave microchannels were fabricated using wet etching. A titanium dioxide suspension was deposited on the microchannel wall as the catalyst. The aqueous methylene blue (MB) solution was used as a model pollutant to demonstrate the performance of photocatalytic test system. Experimental results confirm the presented photocatalytic microreactor is an effective device to detect pollutant in water.