The continuous flow process of liquid phase oxidation to glyoxylic acid was studied in a microchannel reactor using glyoxal and hydrogen peroxide as raw materials.The effects of material ratio, catalyst dosage, hydrogen peroxide concentration, residence time and temperature on the reaction were investigated.The optimized reaction conditions are: n(glyoxal)∶n(H2O2)∶n(FeSO4)= 1∶1∶0.13, the hydrogen peroxide concentration 1.67 mol/L, residence time 10 min, and reaction temperature 30℃. Under the above-mentioned reaction conditions, glyoxal conversion rate reaches94.7%and the glyoxylic acid selectivity reaches 85.4%.This process takes full advantage of the excellent mass and heat transfer characteristics of the microchannel continuous flow reactor, greatly shortens the reaction time, increases the reaction rate, expands the selection range of the process conditions, realizes the effective control of the oxidation reaction process, and increases the safety factor.