Objective To analyze the drop-out rate, characteristics of drop-outs and the causes leading to premature discontinuation of sublingual immunotherapy (SLIT) in allergic rhinitis (AR).Methods Clinical data of 343 AR patients who received SLIT in our department from May 2018 to Aug 2018 were collected by telephone follow-up and analyzed retrospectively. All the patients were divided into 5 groups based on the age (3~6 years old, preschool group; 7~12 years old, school group; 13~20 years old, puberty group; 21~40 years old, adolescent group; 41~60 years old, middle-age group).Results ①Of the 343 patients, 299 (194 males and 105 females) had complete follow-up data and aged from 4 to 52.The case numbers of preschool, school, puberty,adolescent and middle-age groups were 27, 91, 104, 66 and 11, respectively;②The drop-out rate was 51.17% at the first 6 months, 59.20% at the first year and 74.25% at the second year. Most patients terminated SLIT at the third and the fourth month of treatment. There was no difference of the drop-out rate between the male and the female groups, and the differences of the drop-out rate among different age groups were all statistically insignificant; ③Seven patients (3.15% of the drop-out cases) terminated the therapy because of adverse reactions; ④The top 4-ranked causes of drop-out were the long course of treatment, perceived efficacy of treatment, inconvenience of getting the prescription, and cost of drugs.Conclusions The drop-out rate of SLIT for AR is quite high, and the most drop-outs happen at the third and fourth month of the therapy. Neither age nor gender has an significant effect on the drop-out rate. Enhancing education of patients, strengthening follow-up and extending the duration of the first prescription may help to reduce the drop-out rate of SLIT.