Sensor networks are widely used in environment exploration and disaster recovery and in military applications due to their self-organization characteristics and distributed nature. As a fundamental requirement for providing security functionality in sensor networks, key management plays a central role in authentication and encryption. In this paper, we present a hexagon-based key predistribution scheme and show that it can improve the key management in sensor network through the use of the bivariate polynomial in a hexagonal coordinate system based on deployment information about expected locations of the sensor nodes. We show that the scheme presented here can improve the probability of establishing pairwise keys between sensor nodes of up to two hops apart by more than 40% over previous schemes.