Top synthetic spin valves with structure Ta/NiFe/CoFe/Cu/CoFe(P1)/Ru/CoFe(P2)/FeMn/Ta on Si(100) substrate with natural oxide were prepared by dc magnetron sputtering system, and investigated on the magnetoresistance properties and effective exchange bias field. As the thickness of FeMn increased above 150 $AA$, MR ratio was decreased due to the current shunting effect. As the thickness of free layer decreased below 40$AA$, MR ratio was reduced rapidly. In case of 40 $AA$ thick of free layer, spin valve film with a structure Si(100)/Ta(50 $AA$)/NiFe(27 $AA$)/CoFe(13 $AA$)/Cu(26 $AA$)/CoFe(30 $AA$)/Ru(7 $AA$)/CoFe(15 $AA$)/FeMn(100 $AA$)/Ta(50 $AA$) exhibited maximum MR ratio of 7.5 % and an effective exchange bias field of 600 Oe, respectively. Thickness difference dependence in this synthetic spin valve structure on effective exchange field was investigated and interpreted by the analytical method. It should be noted that thickness increase of CoFe(P 1) and decrease of CoFe(P2) in synthetic antiferromagnet leaded to the decrease in effective exchange bias field by experimentally and analytically.