Abstract: Objective To study the effect of number of microscope field of view  on the manual counting of white blood cells (WBC) and platelets in the blood smear, and to standardize the parameters and methods used in microscopy for cell counting. 
Methods The WBC and platelets of 300 peripheral blood samples were calculated by three different methods: automatic hematology analyzer (AHA) method, neubauer hemocytometer and blood smear method. The WBC and platelets were calculated by microscope with field of view of 20 and 26.5 respectively, and the results were collected for comparison and cell estimation. 
Results The platelet count per every oil field of view of the microscope and WBC count with a field of view of 20 were lower than those of the microscope with a field of view of 26.5, and the difference was statistically significant (P＜0.05). The normal and high values of the WBC count estimated by a microscope with a field of view of 20 were lower than those of AHA and neubauer hemocytometer. The normal, low and high values of the WBC count estimated by a microscope with a field of view of 26.5 were lower than those of AHA and neubauer hemocytometer, and the difference was statistically significant (P＜0.05). When R=10, the normal and high values of platelet count estimated by a microscope with a field of view of 20 were lower than those of AHA and neubauer hemocytometer. The normal and high and low values of platelet count estimated by a microscope with a field of view of 26.5 were lower than those of AHA and neubauer hemocytometer, and the difference was statistically significant (P＜0.05). When R=15, the normal value, low value and high value of platelet count estimated by the microscope with field number of 20 and field of view 26.5 were higher than those of AHA and neubauer hemocytometer, and the difference was statistically significant significance (P＜0.05). When using the platelet estimation formula for microscopes with fields of view of 20 and 26.5, compared with AHA and neubauer hemocytometer, there was no significant difference in the three concentrations of specimens (P＞0.05). 
Conclusion Different field of view microscopy has an effect on the counting of WBC and platelets. The microscope with 20 field of view has reference significance for the platelet count of low value specimens when R=10 and the microscope with 26.5 field of view when R=7.33. The microscope with 20 field of view has reference significance for WBC counting in low value specimens. The platelet estimation formula is applicable to the counting of low, normal and high value samples for microscopes with two different field of view. 

Key words: white blood cell count, platelet count, microscopy ,