Key establishment plays a central role in authentication and encryption in wireless sensor networks, especially when they are mainly deployed in hostile environments. Because of the strict constraints in power, processing and storage, designing an efficient key establishment protocol is not a trivial task. Also, it is infeasible to apply public key techniques onto large-scale wireless sensor networks. Most of proposed solutions are based on symmetric key techniques and mainly focused on key predistribution mechanism. In this paper, we present a new key predistribution scheme using bivariate polynomial combining with expected deployment knowledge. We show that our approach takes advantage in terms of resilience against node compromised over prior schemes with the same resource requirements.