By the study of Linux drivers in a symmetric multiprocessor（SMP） environment and according to requirements of asynchronous calls at user level， a high real-time and large-throughput encryption multi-card driver design is presented. The drivers receive the packets from user level and send them to encryption card. An interrupt is triggered to notify drivers to receive the data processed by on-board dedicated encryption chips for power network. The packets are inserted into encrypted/decrypted packets queue for user's asynchronous read. In parallel process of multiple encryption cards， different users can call encryption module with several device operation handles to read and write the encryption card asynchronously. At the same time， taking into account SMP environment， this asynchronous reading and writing operations are synchronized so as to proceed orderly. Test results show that the discussed mechanism may provide an effective method implementing parallel drivers.