Analyzed comprehensive effects of glass surface and glass, when combined with residue that have different water content, on incident ray, designed a instrument that can detect brightness of reflex. Take normal distilled spirit residue, beer residue, vinegar residue as sample. Use electrical fan dryer to make dry residue sample which contains almost 0% of water, use electrical scale, measuring cylinder, burette, blender, atomizer to make residue samples which contain 10%, 20%, 30%, 40%, 50%, and 60% of water. Put residue samples have different water content under a piece of glass, put double-D fiber sensor perpendicularly to the glass, one fiber is used to output ray signal, the other one is used to receive ray signal: read, record, and process light signal from residue samples with different water content. Seen from three data of residue experiments: Three types of residue's comprehensive effect on incident ray is nonlinear. Three types of residue have the strongest effect with 20% of water content. Experimental results are used to develop detecting instrument.