In wireless sensor networks (WSNs), congestion may occur when sensor nodes are densely distributed and/or burst a mass of data flows, the congestion tends to cause packet loss, which sequentially causes lower throughput and wastes energy. To address this challenge this paper proposes a new congestion control scheme, Phase-divided TCP (PTCP), for wireless sensor networks. It controls the congestion through phase-divided adjusting of the growth rate of the TCP window in the slow-start. Our simulation results demonstrate that the proposed scheme can dramatically resolve congestion control problem, and improve TCP performance of wireless sensor networks.