In recent years personal health monitoring Body Sensor Network (BSN) have got significant importance. Due to its sensitive and constrained nature, health data should be transported / kept confidentially, therefore, lightweight cryptographic technique and key management schemes are required in BSN. In this paper we have proposed a hybrid authenticated key agreement with rekeying for Body Sensor Network. Our scheme is based on Symmetric and Elliptic Curve Cryptography. The proposed scheme reduces seventy four percent memory requirements for keys storage, eighty seven percent Computation Cost and sixty one percent Communication Overhead.