Consulting the indirect comparison protocol of Standard Reference Photometer（SRP) from BIPM(Bureau International des Poids et Mesures) and U.S.EPA（Environmental Protection Agency),the indirect comparison technique of SRPs was developed by preparation of pre-comparison,confirmation of comparison procedure,treatment of comparison results and evaluation of comparison index through the ozone transfer standard.Furthermore,SRPⅠand SRPⅡ were indirectly compared,while the slopes of the two indirect comparison equations between SRPⅠand SRPⅡ were 1.003 26 and 1.003 58 with the intercepts of 0.109 05 nmol/mol and 0.080 99 nmol/mol,respectively,which indicated that there was a good consistency between the two SRPs,and the indirect comparison results could meet the comparison index of SRPs by U.S.EPA.The indirect comparison method of SRPs was established,and it was suitable for the comparison between SRPs.