Abstract: Objective To verify the analytical performance of the BD FACS Canto Ⅱ flow cytometer in the absolute counting of lymphocyte subsets. Methods According to the documents provided by the China National Accreditation Service for Conformity Assessment (CNAS), the Clinical and Laboratory Standards Institute (CLSI) Evaluation Protocols, and the Health Industry Standard of China, the analytical performance of the BD FACS Canto Ⅱ flow cytometer was evaluated in terms of precision, accuracy, linearity, carryover, and reference range. Results For absolute counting of CD3⁺ T cells, CD3⁺CD4⁺ T cells, CD3⁺CD8⁺ T cells, B cells, and NK cells, both CV of within-run and between-run precision were less than 10%. The measurement bias values of all lymphocyte subsets were lower than the assigned uncertainty. The linear fitting coefficient (R²) for absolute counting of each subset was above 0.990, meeting the manufacturer's declared linearity requirements for clinical testing. The carryover contamination rates for all subsets were <5%. In the reference interval verification, the correlation coefficients (R values) for both relative percentages and absolute counts of lymphocyte subsets were ≥90%, consistent with the manufacturer's reference intervals. Conclusions The BD FACS Canto Ⅱ flow cytometer demonstrates good analytical performance in the absolute counting of lymphocyte subsets, meeting clinical diagnostic requirements and suitable for relevant laboratory testing.