Interference alignment is used to maximize the sum capacity of the interference channel. Relay nodes can be used in multi-hop interference channels which will aid in long range transmission. For the multiple-antenna decode-and-forward relay interference channel, this paper proposes a relay-aided interference alignment algorithm. Each node is equipped with multiple antennas and has a message symbol to be transmitted to its destination partner in a one directional communication between K node pairs. In terms of bit error rate, numerical analysis show that the proposed algorithm is better than other strategies. It is shown that as the number of hop increases, the performance degradation of DF relay systems is due to error propagation.