Abstract: Objective: To explore the clinical features,cytopathological morphology,immunophenotype and differential diagnosis of primary thyroid non-Hodgkin's lymphoma (NHL) and gather experience for diagnosis.Method: Reporting two cases of primary thyroid non-Hodgkin's lymphoma,reviewing corresponding references,analyzing the clinical manifestation and iconography features of primary thyroid NHL,observing the cytopathological morphology,and analyzing the differential diagnosis.Result: Case 1:58-year-old male was found thyroid mass 4 years ago which could move with swallowing and was diagnosed as Hashimoto thyroiditis. Ultrasound showed enlargement of thyroid and bilateral cervical lymph nodes. Fine needle aspiration from isthmus mass showed diffusely immature lymphocytes. Then suspicious non-Hodgkin's lymphoma was diagnosed and isthmus mass lumpectomy was done. It was diagnosed as diffuse large B-cell lymphoma. Immunophenotype:CD20,CD79a,PAX-5,Bcl-6,Bcl-2,Mum-1(+);Cyclinol,PD1,Cxclb,CD30,ALK,TdT,CD15,CD3,CD4(-),Ki67LI(≈80%). Case 2:25-year-old female,pregnancy in the 4th month,was found right-side thyroid mass 4 months ago,with quick enlargement in the last month. Ultrasound showed uneven enlargement of right lobe. Fine needle aspiration from thyroid mass showed diffuse round tumor cells in microscope, containing small nucleoli and rare mitosis. Cytopathologic characteristics suggested the diagnosis of non-Hodgkin's lymphoma and lumpectomy was performed. Then it was diagnosed as B cell lymphoma (high invasive) pathologically and consistent with the feature of Burkitt Lymphoma. Immunophenotype:CD20,PAX-5,CD43,Bcl-6,CD10,Mum-1(+),Bcl-2 weakly positive CD3,CD5,CD21,CD23,TdT,CD99,CD34(-),Ki67LI>95%.Conclusion: Primary thyroid non-Hodgkin's lymphoma is rarely seen,which should be differentiated with Hashimoto thyroiditis,medullary carcinoma (small cell variant) and general lymphoma with thyroid involved.