In this paper, we propose a distributed traffic-aware routing system for wireless sensor networks with multiple sinks. In multisink networks, traffic moving toward one sink may congest that moving toward others. The algorithm presented here considers the traffic of surrounding neighbors before jumping to any sink. We accomplish this by building, for each single sink, a gradient field and using gradient search for routing. The gradient index of one node contains two parts. (1) The first represents the distance-cost to travel, based on ROLL (routing over lossy link) proposed by an IETF working group. (2) The second contains the implicit traffic delay carried by the current holding node. Gradient field is built in distributing way and proved to free from loop. By simulation, we show that this method of building gradient field routes balance between shortest path and possible congestion made by sinks, especially in heavy traffic networks, thereby reducing the overall end-to-end delay.