Static and dynamic magnetic properties of exchange-biased FeCo/MnIr multilayers were systematically investigated. A huge increased ferromagnetic resonance frequency up to 10GHz was observed in the case of thin MnIr layers being possibly interpreted as the contribution of the rotatable anisotropy. The rotatable anisotropy as well as the resonance frequency and frequency linewidth can be tuned by changing the thickness of MnIr layer. The correlation between the variation of rotatable anisotropy and enhancement of coercivity and magnetic damping is discussed.