【Objective】 To analyze parainfluenza virus (PIV) infection of children with respiratory tract infections (RTI) and the relationship between neutropenia in Xi'an. 【Methods】 Specific IgM of PIV with Enzyme-linked immunosorbent assay (ELISA) was detected.Peripheral blood leukocytes were detected by hematology analyzer. 【Results】 PIV infection in 1~6 years age group were significantly higher than other age groups,neutropenia in 1~3 years age group were higher incidence of disease,PIV infection was closely related with neutropenia. 【Conclusions】 PIV infection with respiratory tract infections are higher among children in Xi'an.It is very useful for clinicians selecting efficient drugs to detect Specific IgM of PIV in routine test in the children of RTI.