Abstract: 20% (W/V) meglumine solution was neutralized to pH7.2 by adding amidotrizoic acid and diluted with saline in a volume ratio of 1:1, 1:1.5, 1:2, 1:3, 1:4 and 1:5 to form different density gradient solutions, then added into a test tube separately.Heparinized infected mouse blood was centrifuged and the blood cell pellet was transferred to the top of density gradient. After centrifugation at 2 500 rpm for 25 minutes, the sample was separated into seven layers, free parasites and the red cells infected with parasites of different stages being in the upper five layers and the uninfected RBC and WBC mainly in the lower two layersThe infected RBC were collected and washed once with saline, then 37 ℃ warmed 0.8% NH4Cl solution was added to lyse RBC membrane. Incubate the suspension at the same temperature for 10 minutes, and then centrifuge down the free parasites at 2 500 rpm. After washing with saline and eliminating the sticky residue in the bottom of the centrifuge tube the purified parasites were harvested, and only one or two white blood cells could be found per 104 parasites with a limited amount of ghost corpuscles.