Network coding techniques offer a new solution to data transmission in Delay Tolerant Networks (DTN). To date, much work have been done on network coding based schemes for DTN, however, most of them bring additional overhead due to the extra coded packet redundancy. In this paper, we propose NTC, An efficient Network Coding scheme for DTN. In NTC, a novel metric named "redundancy ratio" was proposed to evaluate the redundancy of a new coded message, and the nodes forward message by exploiting the information of "redundancy ratio". To evaluate the performance of our proposed NTC scheme, we implement NTC in ONE, the current state-of-the art simulator. Simulation results shows that, comparing with existing schemes, our proposed NTC scheme has significant advantages in enhancing the message delivery ratio whereas reducing the transmission overhead.