A novel microchannel synthesis route for continuous synthesis of nanosized copper iodide (gamma-CuI) using hydrated hydrazine as reducing agent was proposed. We continuously produced gamma-CuI spherical nanoparticles in 99% yield and grain size of ca. 44-100 nm. Furthermore, the utilization of hydrated hydrazine was essential in precluding powder plugging the microchannel by self-generated N-2. The microreaction process conditions, such as residence time, pH value, temperature, and reactant concentration, had great impact on the crystal phase and grain size. The optical properties analysis showed that red-shift in band age and emission intensity of photoluminescence spectra at 428 nm decreased with decreasing grain size. Moreover, the nanosized spherical gamma-CuI exhibits enhanced photocatalytic performance in the photodegradation of methylene blue and methyl orange.