Exchange biasing and coercive field of molecular-beam-epitaxy-grown Fe/Fe50 Mn50 bilayers have been investigated by Surface Magneto-optical Kerr Effect(SMOKE) and ferromagnetic resonance measurements. The results indica te that there is no exchange biasing when the thickness of antiferromagnetic lay er is less than 55nm. The exchange biasing appears when the thickness of antif erromagnetic layer is greater than 55nm，and the maximum value is reached when the thickness is about 7nm. Exchange biasing and coercive field decrease with f urther increase of the thickness of the antiferr-magnetic layer. The ferromagnet ic resonance measurement results show that there exists unidirectional anisotrop y. The above results are discussed in the paper.