Abstract: Objective To analyze the causes of pseudothrombocytosis by hematology analyzer and explore the methods to count platelet accurately. Methods A total of 14 cases of pseudothrombocytosis were retrospective analyzed. All the specimens were used to prepare blood smears and the platelet count and distribution was observed under a microscope. The platelet count was re-examined by PLT-O and manual count. Results All the samples showed pseudothrombocytosis, with abnormal platelet histograms. The results of blood smear by microscopy were inconsistent with instrument counting. There was no statistical difference between the results of PLT-O and manual count(P>0.05). Conclusions When platelet histogram is abnormal, it is necessary to identify the presence of factors that interfere with platelet count, pay attention to microscopy, and perform PLT-O/PLT-F or manual platelet count if necessary, so as to ensure the accuracy of platelet count.