In this paper, thetheoretical study and measured technique for the banknote of the reflection light and thetransmission light are introduced. After the contrast experiment, the characteristicdifferences of the true and false banknotes are discovered. The check circuit and checksystem of the transmission and reflection light were developed with making use of thecharacteristic difference in the pertinence. The banknote was checked and recognised withthe check system. The technology was directly used to doing of finance instrument. Therecognizing technology and falsing technology of the banknote will be advanced in thefinance instrument. The technique is very applicable.