In this paper, a reasoning model is proposed for energy efficiency task allocation in wireless sensor network. The presented energy efficient contract net protocol is used to implement the negotiation process. Multi-issue scoring function can evaluate the offer with multi-issues in a quantifiable way. An energy threshold is brought to decrease communications which will turn out to decrease nodes’ energy consumption. And the usage of energy threshold also promote the nodes with high level energy have more chance to implement tasks. The simulation results show that the allocation model has outstanding performance maintaining a fair energy balance and is energy efficient in negotiation process.