| The experiment was carried out in 2001 and 2002. Four plum cultivars, i.e. Dashi early ripening, Longyuanqiuli, Fraiar, Angeleno, were used to investigate the changes of anthocyanin, chlorophyll, carotenoids, total phenolics, flavonoids, main sugar concentration and PRO activity. Moreover, various pigment substance (such as anthocyanin, chlorophyll, carotenoids, flavonoids) were studied when matured.The result showed that, anthocyanin, main sugar concentration and PPO activity increased along with the chlorophyll, carotenoids, phenolics, flavonoids concentration decreased during the plum development.Pigments concentration in fruit peel was higher than that in flesh, in addition, the plum fruit color was determined by the concentration of anthocyanin. The concentration of phenolics was changed along with the accumulation of PPO activity. The outcome exhibited brown. The color appearance was determined by this substance together with anthocyanin, chlorophyll, carotenoids, flavonoids. The pigments concentration in peel was greatly higher than that in flesh.To understand the mechanism of anthocyanin synthesis, one approach is to investigate the difference between HCl-methanol method and pH-differential method. Accumulation of anthocyanin used in pH-differential method paralleled with that in HCl-methanol method. Moreover, marked positive correlationship was confirmed between the two methods. Additionlly, The OD of HCl-methanol extract amounted to the sum of that of red filtrate after removel of methanol and solution of browning precipitate in HCl-methanol. So pH-differential method was accepted in this experiment. Also, the browning deposit influenced the color of plum fruits.There were close relationships among anthocyanin concentration and carotenoids, flavonoids, total sugar, sucrose, fructose, glucose concentration. There was close negatively relativity between anthocyanin and carotenoids in cv. Longyuanqiuli (r=-0.9295*) and Fraiar (r=-0.8822*) , between anthocyanin and flavonoids in cv. Dashi early ripening (r=-0.9644**) and Angeleno (r=-0.9094*) . Except relation between sucrose, glucose contents and anthocyanin content in Angeleno, there wasmarked correlation between anthocyanin and total sugar, sucrose, fructose, glucose. There was marked relation between sucrose and anthocyanin in cv. Dashi early ripening( r= 0.9688**) , cv. Longyuanqiuli (r= 0.9481*) , Fraiar (r=0.9447*) ; between anthocyanin and fructose in cv. Dashi early ripening ( r= 0.9438**) , cv. Longyuanqiuli(r= 0.9763**) , cv. Fraiar (r=0.9358*) , cv. Angeleno (r=0.8925*) ; between anthocyanin and glucose in cv. Dashi early ripening ( r= 0.8940*) , cv. Longyuanqiuli(r= 0.9022*) , cv. Fraiar (r=0.9424*) . Total phenolics had been showed to be negatively correlated with PPO activity in cv. Longyuanqiuli ( r= -0.9896** )and Fraiar peel ( r= -0.9664**) , In addition in cv. Dashi early ripening ( r= -0.8562*) and Angeleno ( r=-0.8601*) flesh.Carotenoids and flavonoids may be participating in anthocyanin metabolism, for their concentration decreased along with anthocyanin accumulation during fruit development. Anthocyanin synthesis was on the base of sugar metabolism. So enough sugar (total sugar, sucrose, fructose, glucose) concentration is very important to anthocyanin synthesis. The technical measure that propitious to sugar accumulation accelerated to anthocyanin synthesis.Anthocyanin concentration was very low on the early stage of fruit development, and reached maximum when matured. From these, we should actualize the measure that facilitated anthocyanin accumulation, such as paving glisten film, removing leaf, rotating fruits, little making use of nitrogenous fertilizer, little use of water and more kalium fertilizer. Further, The accumulation of sugar was mostly in the stage of flesh rapid growth.' Moreover it reached maximum in maturation. There was variance of main sugar concentration in different plum fruits. For example, more making use of organic fertilizer, kalium fertilizer, reasonable loading facilitated...
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