The effects of carbohydrates on the toxicity of p-Aminophenyl arsenoxide (p-APAO) against S. cerevisiae were investigated by Microcalorimetry, including glucose, fructose, lactose, sucrose, N-acetyl glucosamine, 1,3,4,6-tetra-O-acetyl-D-glucosamine (OADG), and chito-oligomer. The toxicity of p-APAO on S. cerevisiae decreased in the presence of OADG or chito-oligomer. Among the test carbohydrates, the antagonism of OADG was better than those of other sugars. These results suggested that OADG and chito-oligomer were p-APAO antagonists. Carbohydrates could form complex with p-APAO to prohibit p-APAO from polymerizing. This result was attributable to hexose carriers not recognizing the p-APAO effectively.