The paper reports the diagnosis and treatment of a old female canine with mastocytoma.The conditions of the canine were evaluated comprehensively by clinical examination,blood biochemical examination,cytological examination,imaging examination,and histopathological examination.Surgical treatment was used,including tumor removal and splenectomy.The canine healed well after operation without obvious adverse reactions.The results suggest that the diagnosis and treatment of canine mastocytoma requires a combination of various methods,including clinical examination,laboratory examination and surgical treatment.Early diagnosis and comprehensive treatment can improve the prognosis of dogs and reduce the recurrence rate.At the same time,pet owners should pay attention to the living environment and habits of pets to reduce the risk of illness.