BN nanosheets (BN) have drawn great attention in heterogeneous catalysis recently, and their defects have a profound effect on the key performance of the catalyst, but it has been overseen and little addressed. Here, three Fe/BN nanosheet (Fe/BN) catalysts were prepared BN with varied B-O surface defects. Fischer-Tropsch synthesis, a key industrial process, was taken as an example. It is found that the rich B-O defects not only resulted in decreased crystal size and low crystallinity of the Fe2O3 but also showed enhanced interaction with the active component and support. As a consequence, the three Fe/BN catalysts showed a dramatic difference in catalytic performance. Our studies reported here could be a guide for the rational design of the highly efficient hydrogenation BN-based catalyst.