Ring-opening copolymerization of phthalic anhydride (PA) with propylene oxide (PO) was successfully carried out by using double-metal cyanide (DMC). The characteristics of the copolymerization were presented and discussed．The structure of the copolymer was characterized with IR and 1H-NMR. The number-average molecular weight (Mn) and molecular weight distribution of the copolymer were measured by GPC. The results showed that DMC was a highly active catalyst for the copolymerization of PA and PO

giving high yield with a rate much higher than that of PO homopolymerization with the same catalyst at a low catalyst level of 60 mg／kg．This copolymerization can be also carried out in many organic solvents

and it was easier to be carried out in polar solvents such as THF and acetone than in non-polar solvents such as ether and cyclohexane．The proper temperature for reactions carried out in solutions was in the range of 90 ～ 100℃. That was lower than the temperature range for bulk-copolymerization．The Mn was affected by the catalyst level

reaction temperature and trace water．Mn was in a range of 2500～4000 under firm polymerization conditions by removing trace water and other impurities．The kinetics of the copolymerization was also studied．The results indicated a first order relationship between the copolymerization rate and the monomer concentration.