In mobile environment of wireless sensor networks (WSN), the fixed frame of MAC protocol causes performance degradation such as packet collision due to overloading etc. In this paper an optimal load and mobility aware MAC protocol for WSN is proposed. Each node measures the received signal strength (RSS) from the receiver by monitoring the acknowledgement packets and based on the RSS value, the link quality and mobility of the node can be predicted. Depending on the predicted link quality and mobility, the relay node selection process is initiated. In relay node selection process the neighbors with minimum load and good RSSI values is selected as the relay node. The moving source then transmits the packets through this relay node. This protocol reduces the packet drop due to overload and weak link quality. By simulation results, it is shown that the proposed approach minimizes the energy consumption.