Computer-based patient record is the most important part of electronic medical information. The main problem for applying computer-based patient record is how to share patient information safely and protect patient privacy in the meantime. In this article, the safe sharing issues of computer-based patient record are described. The principle of dynamic password is described and an access control system based on dynamic password is designed. Dynamic password (one time password) can be produced by software, mobile phone and electric token according to the user safety level and different request of user. This identity authentication system based on dynamic password can be easily merged into most of hospital information systems. By using this technology, computer-based patient record can be shared by different organizations safely, quickly and conveniently. In the meantime, the patient privacy can be protected very well also.