Two-dimensional code is our common barcode, which is widely used in domestic logistics industry. Modern express companies will print bar codes on express waybills, and carry out information management on express mail from the place of origin to the destination, effectively ensuring the timeliness and safety of express mail, reducing the operating costs of enterprises and facilitating customers to inquire about express mail. The premise of using bar code is that enterprises must install a complete information management system (hardware and software) as the basis of bar code information input and storage. Barcodes are usually used in combination with hand-held scanners. The origin station inputs basic information and delivery information, the transfer station inputs arrival information and delivery information, and the destination station inputs arrival information and receipt information. In this way, the whole information record of cargo transportation is completed. Recognition principle of bar code: To convert the bar code compiled according to certain rules into meaningful information, it needs two processes: scanning and decoding. The color of an object is determined by the type of light it reflects. White objects can reflect various wavelengths of visible light, while black objects absorb various wavelengths of visible light. Therefore, when the light emitted by the light source of the barcode scanner is reflected on the barcode, the reflected light shines on the photoelectric converter inside the barcode scanner, and the photoelectric converter converts it into corresponding electrical signals according to the reflected light signals with different intensities. The electrical signal is output to the amplification circuit of the barcode scanner to enhance the signal, and then sent to the shaping circuit to convert the analog signal into a digital signal. The widths of white bars and black bars are different, and the duration of corresponding electrical signals is also different. Then, the decoder determines the number of bars and spaces by measuring the number of pulse digital electrical signals 0 and 1. By measuring the duration of 0, 1 signal, the width of bars and spaces can be judged. The data obtained at this time is still quite confusing. In order to know the information contained in bar code, it is necessary to convert bar code symbols into corresponding digital and character information according to the corresponding coding rules (such as EAN-8 code). Finally, the detailed information of the article is identified by the computer system, and the data is processed and managed.