Objective　To explore the diagnostic value of the ratio of α1-microglobulin to microalbumin in acute interstitial nephritis. Methods　Data were collected from 12 childhood acute interstitial nephritis patients from Jan. 1, 2014 to Dec. 31, 2017. The ratio of α1-microglobulin to microalbumin, and urine protein electrophoresis were monitored and analyzed. Each 10 cases of Dent disease, nephrotic syndrome, IgA nephropathy, Henoch-Sch?nlein purpura nephritis, lupus nephritis and Alport syndrome were included at the same duration as control group. Results　In all the 12 cases, α1-microglobulin was increased apparently, the ratio of α1-microglobulin to microalbumin was much higher than 1, and was closely related to the percentage of low molecular weight protein in urine protein electrophoresis (P<0.05), the same as Dent disease, while the ratio was about zero in other glomerular disease groups. Conclusions　The ratio of α1-microglobulin to microalbumin, if over 1, can be used as a diagnostic criteria for tubuloproteinuria.