The purpose of this research is measuring and comparing service quality and ranking its dimensions in Melli bank branches of Esfahan city. For attaining this purpose SYSTR-SQ scale is used. This scale is special for measuring bank service quality. Questionnaire drive from this scale is contained four dimensions and 21 question. Dimensions are service system quality, behavioral system quality, service transactional accuracy and machine service quality. Population is branches of Melli bank of Esfahan city. 14 branches has been selected from them with cluster sampling and then sampling of customers was accomplished. In sum 534 customers answered to questions. With analyzing data collected results indicates that service quality and its dimensions have favorite status. Also branches with different quality degree, have no difference in service quality. Finally results in ranking dimensions indicates that dimensions service transactional accuracy and behavioral system quality are in first and second rank and service system quality and machine service quality are in the next rank.