Based on the spectral absorption/reflection principles, a home-made optic sensor which included substrate, filtration membrane, reaction film and absorbent pad has been proposed and established to detect vitamin C rapidly. In the experiment, ferric ion was reduced to ferrous ion by vitamin C in samples, the reaction film color turned from yellow to orange-red upon the binding reaction of ferrous ion to phenanthroline. Results demonstrated that vitamin C concentrations were proportional to L values of the L a b color system. A good linearity was presented in the range of 0.25-2500 μg/mL. The correlation coefficient(r) was 0.980 and the testing time was about 2 min at room temperature.