By adjusting the Cr concentration, the effect of texture and grain size on the exchange bias of NiFe/PtMn bilayers with (Ni0.81Fe0.19)1-xCrx seed were systematically investigated. After annealing the bilayers at 270℃ for 5h, it was found that the difference in the texture of PtMn layer is not the cause of the variation in the exchange bias field. The exchange bias field depends strongly on the grain size of PtMn layer. When the grain size is around 11.3nm, the exchange field attains its maximum.