Hydroxyl radicals from Fenton reaction can react with salicylate to form 2,3-dihydroxybenzoate.The quantitative analysis of hydroxyl radicals can be done through the colorimetric determination of 2,3 -dihydroxybenzoate.The determination condition has been studied and a best determination program has been obtained. The test indicated that hydroxyl radicals from this system could be scavenged by reutin and quercitin.This system can be used as a convenient method for the selection of hydroxyl radical scavenger.