Abstract— This paper proposes and evaluates a new aggregation algorithm in wireless sensor networks with time constraint. In the proposed algorithm, each aggregation node controls its aggregation time in order to aggregate and transfer data from child nodes within a given deadline of the sink node. The objective of the algorithm is to deliver the time constrained data within time bound while reducing the energy consumption resulted from the number of transmissions. Based on the aggregation tree, the proposed algorithm considers the number of the child nodes to determine the aggregation time. The performance of the proposed algorithm is evaluated using both the miss ratio and the aggregation gain.