We report the effect of Ru(seed-layer) on the interlayer antiferromagnetic coupling field Hexex, and coercivity Hcc in the Cr/Ru(se ed-layer)/PtCo(thermal stabilizing layer)/Ru(spacer layer)/PtCo(recording layer)/Ru(protective layer) films. Both Hexex and Hcc increase with t he increase o f the thickness of the seed-layer Ru. It arises probably from the appearance of hcp structure in the seed-layer Ru. Hexex and Hcc sh ow a peak value at Ru(seed-layer) layer with a thickness of ～08nm.