The influencing factors on cord blood storage after collection and mononuclear cell separation as well as cryopreservation were studied. The mononuclear cell are separated from blood after blood collection, then cryopreserved and washed after thawed. Results showed that the cord blood kept at 4 degrees C or room temperature less than 24 hours after blood collection, mononuclear cell separated by hydroxyethylstarch and 2 centrifugations, mononuclear cell cryopreserved with 50% DMSO and autoplasma from cord blood as protectives and washing the cells after thawing. In conclusion, the optimal project in this study can effectively preserve cord blood mononuclear cells.