Electron and spin transport in chiral antiferromagnets are of great interest in both fundamental and application point of views. In this letter, we explore and compare spin transport properties of a chiral antiferromagnetic L12-ordered Mn3Ir and a disordered Mn3Ir by the spin pumping experiments. Larger Gilbert damping enhancement of the Fe20Ni80 was found in L12-ordered Mn3Ir/Fe20Ni80 and L12-ordered Mn3Ir/Ti/Fe20Ni80 multilayers comparing to those with disordered ones. Our results suggest that the chiral spin structure causes larger spin dissipation than disordered spin structure.