Objective:To observe the outcomes of different cooling rates in the cryopreservation of platelets,so as to screen the best cooling rate for cyropreservation of platelets.Methods: Platelet concentrate was cooled down with the new cryopreserving solution at various cooling rates(1,10,20℃/min) and was kept at -80℃ for one week．Then platelets were thawed to check platelet count，adrenaline induced aggregation，and expression of CD41,CD42b and CD62p; the results were compared with those of the non-programmed cooling group and fresh platelets.Results: The platelet counts of cryopreserved groups were lower than that of fresh platelet concentrate(P<0.05 or P<0.01).There were no differences in adrenaline induced aggregation between 10℃/min group,1℃/min group,and non-programmed cooling group; and the aggregation of the former 3 groups was lower than that of 1℃/min group(P<0.01) and higher than that of 20℃/min group (P<0.05).The CD42b expression in 10℃/min group was higher than in other groups (P<0.05) and lower than in fresh platelet concentrate.The CD62p expression in 1℃/min group,20℃/min group,none programme cooling group was higher than in fresh platelet concentrate(P<0.05).The CD62p expression in 10℃/min group was higher than other 3 groups (P<0.05) and lower than in fresh platelet concentrate,with no statistical significance.Conclusion: Cooling rate has great impact on the quality of cryopreservted platelets.Compared with 1℃/min and 20℃/min,10℃/min is the optimal cooling rate with the new cryopreservation solution in this study.