In this paper, we propose a reconfigurable adaptive FEC system. In adaptive FEC schemes, the error correction capability t is changed dynamically according to the Communication channel condition. If a particular error correction capability t is given, we can implement an FEC decoder which is optimal for t by taking the number of operations into consideration. Thus, reconfiguring the optimal FEC decoder dynamically for each error correction capability allows us to maximize the throughput of each decoder within a limited hardware resource. Based on this concept, our reconfigurable adaptive FEC system can reduce the packet dropping rate more efficiently than conventional fixed hardware systems. We can improve data transmission throughput for a reliable transport protocol. Practical simulation results are also shown.