Abstract: In this paper, we analyse 159 cases of FUO children, about 6.76% of hospitalized ill children at same period, FUO morbidity in infants and young children is highest, In the month of 6, 7 or 8 FUO morbidily is 65.4%. The temperature type is commonly irregular, Infectious fever are common （69.81%）, in which septicaemia is 57.65%, the pathogens are mostly staphylococcus and tetraeoceus. FUO children usually have malnutrition, rickets and anemia, ESR over 90mm/h usually show that severe diseases occur. In this paper, we analyse the erroneously diagnostic cases of tuberculosis and leukemia, and take teachings from here. In order to take correct diagnosis, we must recognize normal variation of temperature in healfh chiIdren, differential diagnosis benign and self-limited diseases from severe orgnec diseases, recognize the characteristics of pseudo FUO and long functional fever, and discuss the diagnostic steps of FUO.