Abstract: Objective To certify the linear range of WBC measured by CD3700. Method Use the white stratum of blood after centrifugation as high value specimen. Then, the high value specimens were diluted with physiological saline to get a series of samples with different concentrations. Every specimen was measured twice in order to keep the sequence of specimens randomly. The perform outlier test, polynomial regression analysis, and the random error estimation were carried out. Results There was no outlier in the results. It was demonstrated by polynomial regression to be linear from （0 ~ 219）×109 L-1. The random error was within the allowable limit of 1/4CLIA'88(3.75%). Conclusion The linear range of WBC measured by CD3700 is just like that of the manufacturer claims.