Abstract: Key management is one of the most challenging security problems in wireless sensor networks.Most of the existing key management schemes is supposed used in homogeneous wireless sensor networks in which all the sensor nodes have the same structure and capability.But the homogeneous wireless sensor network does not good at improving the network's life time as well as connectivity.Since there are some different nodes that can establish the same pairwise key between them in some random key pre-distribution schemes,a key management scheme is proposed based on polynomial for heterogeneous wireless sensor networks(HWSN).From the simulations,it is clear that the key management scheme proposed can substantially improve the network connectivity with low storage requirement and enhance the network security level.