With the development and wide application of WSN (Wireless Sensor Network), the information security becomes a serious problem, especially when the WSN applied in military field. Whereas the general WSN routing protocols focus on the transmission efficiency, reliability and energy-efficiency, not on the security. This paper integrates the international popular AES encryption standard, RSA public-key encryption mechanism and digital signature technology to improve classic AODV routing protocol, and shows an SAODV routing protocol which has both energy efficiency and information security. The theoretical analysis and simulation show: when adding security mechanism to AODV in the routing layer, the system owns the defensive ability for the hidden security problem, such as the eavesdropping, coaxing, imitation, replay, denial of service and HELLO diffusion etc and the normal performance of the network almost conform to the AODV protocol.