Abstract: Objective:To study the influence of the storage time of leukocyte depleted erythrocyte suspension on the quality of washed red blood cells by testing the concentration of potassium (K⁺), free hemoglobin (FHb) and calculating hemolysis rate. Method:10 bags of leukocyte depleted erythrocyte suspension preserved for 1 week (1 w group), 2 week(2 w group), 3 week (3w group) and 4-5 week (4-5 w group) were chosen to prepare washed red blood cells manually, and samples were taken to measure (K⁺), FHb and calculate the hemolysis rate at the time 0 h and 24 h after preparation in (4±2)℃. Result:The (K⁺) of washed RBCs at 0 h after preparation of 1 w group, 2 w group, 3 w group and 4-5 w group were (0.38±0.04), (0.44±0.08), (0.53±0.23) and (0.65±0.20)mmol/L, respectively, and 3 w group and 4-5 w group were significantly higher than that of other two groups (P<0.05). And at 24 h after storage the (K⁺) were (1.89±0.32), (1.89±0.60), (2.02±0.45) and (2.62±0.31)mmol/L, respectively, and 4-5 w group were higher than that of other groups (P<0.05). But all the (K⁺) were still lower than the upper limit of (K⁺) in normal human bodies. The FHb and the hemolysis rate of washed RBCs at 0 h and 24 h after preparation of 4-5 w group were significantly higher than those of the other groups (P<0.05). And the FHb of washed RBCs at 24 h after preparation of 4-5 w group was (0.90±0.32) g/L which was significantly higher than national standard. Conclusion:Leukocyte depleted erythrocyte suspension at the end of storage should be avoided to prepare washed RBCs and the prepared washed RBCs should be transfused as soon as possible to reduce the suspension time in saline solution.