Digital Signature System is an indispensible Information Safety Technology for E-commerce, E-government etc. The thesis probed main information safety hazard in the course of information transmission, emphatically explained PKC-based Digital Signature System's realization principle and selective analysised the Digital Signature System how to solve all kinds of potential safety hazard for network information. Finally, through combining Digital Signature with Digital Certificate, elaborated basic process of Internet Information secure transmission.