Peroxidase Isoenzyme (POI) in the matural leaf of 8 citrus biotypes was tested by means of electrophoresis in polyacrylamide gel. The general characterastics of POI profile in citrus leaf and the variation of POI profile in some special biotypes were analysed. It was suggested that the POI analysis can be used to identify some citrus cultivars and variants. In order to approach the relationships among the biotypes, the differences of all biotypes in POI profile were studied quantitatively by ordination using the distance of POI profile.