Abstract: This paper presents a distributed, energy-efficient data gathering and routing protocol for wireless sensor network. In the algorithm, each sensor node is assigned a tier ID in according to the distance between the node and the base station. Nodes closer to the base station are assigned lower tier IDs. When gathering data, nodes with higher tier IDs send their data to their neighbors who have lower tier IDs where the data is aggregated and then forwarded to nodes with even lower tier IDs. Therefore, the communication is conducted at a low energy level, and the data travels, layer by layer, toward nodes with the lowest tier IDs. When the data reaches the nodes with the lowest tier ID, the system selects a node among them to directly communicate with the base station. Because long-distance communication with the base station is energy-consuming, the node sending data to the base station will have its energy drained off very fast so that it die much earlier than other nodes. A mechanism is proposed to shift the long-distance communication among all network nodes, which is called the top-tier shifting mechanism. Using this mechanism, energy consumption can be evenly distributed among all network nodes, and the network lifetime is prolonged.