Abstract: This experiment was to assay the proper reaction of citrus perozidase in the ezocarp of Tankan mandarin (Citus reticulata cv. tankan Hayata) , the proportion of the bound enzyme to the soluble enzyme as well as the distribution of citrus peroxidase in the fruit were also investigated. Samples for this experiment were taken from the flavedo (the colored portion of the exocarp) to test the peroxidase of citrus fruits. A comparisom was made to determine the soluble peroxidase activity among five varieties of citrus fruits growing in Guangdong. The results showed that the correlation between peroxidase activity and storage life of fruits was negative. Tankan mandarin was known as an endemic variety growing in Swatow, Guangdong, because it was a natural hybrid between tangerine and Sweet orange. As shown by the isoenzyme patterns, Tankan, Ponkan and Anliu Sweet Orange, all these three varieties were considered to have cartain filial affinity. Also the relationship between the distribhutiong of peroxidase in the citrus fruits and the fruit juise quality during processing was discussed particularly.