We report the magnetization and electron spin resonance study on charge-ordering (CO) manganite Y0.5Ca0.5MnO3(YCMO) across the charge-ordering transition temperature T-CO down to the antiferromagnetic ordering transition temperature T-N. The transition temperatures of T-CO and T-N are observed at 275 and 125 K, respectively. The observed large decrease in the linewidth from T-N to T-CO can be explained in terms of motional narrowing caused by the hopping of the Jahn-Teller (JT) polarons. Below T-CO the g-value is almost constant, suggesting the weakening of orbital order in the compound of YCMO. (C) 2004 Elsevier B.V. All rights reserved.