In wireless sensor networks (WSNs), power-conserving MAC design is vitally important for sensors which use a power source from a fixed utility or manual battery recharging. In this paper, we propose an energy-efficient sensor selection algorithm with two-hop cooperating transmission, which minimizes the total energy consumption of WSNs by exploiting spatial correlation between sensors without compromising distortion performance. A convex optimization model is set up and we solve this convex optimization problem by adopting a priority ordering method instead of solving complicated equations. The simulation results indicate the necessity of our work for WSNs.