AIM: To detect the expression of interleukin(IL)-36(α, β, γ)in tears of patients undergoing allogeneic hematopoietic stem cell transplantation(allo-HSCT), investigate its correlation with ocular surface microenvironment, and further analyze the relationship between its expression and ocular graft-versus-host disease(oGVHD).METHODS: Prospective study. A total of 35 patients(70 eyes)underwent allo-HSCT in the hematology department of our hospital in January 2020 were selected, and 35 healthy volunteers(70 eyes)with appropriate age and gender were selected as normal control group. The patients in the allo-HSCT group were followed up 3 times after operation once every 3mo. The subjects with postoperative ocular symptoms were divided into oGVHD and Non-oGVHD group.Ocular surface disease index(OSDI)questionnaire, Schirmer test, tear break-up time(TBUT), corneal fluorescein staining(FL), and conjunctival impression cytology(CIC)was conducted in three groups. Furthermore, the expression levels of IL-36(α,β,γ)in tears were detected by ELISA.RESULTS: In the normal control group, IL-36(α, β, γ)expression levels were 74.32±5.27, 70.02±8.43, 97.41±8.66 pg/mL, respectively; in the allo-HSCT group, IL-36(α, β, γ)baseline expression levels were 77.27±7.03, 74.53±7.53, 100.77±9.74 pg/mL, with no statistically significant differences between the two groups(t=1.648, 1.954, 1.262, all P>0.05). There were no significant differences in IL-36α, IL-36β and IL-36γ in Non-oGVHD group at different time points(P>0.05), while there were significant differences in IL-36α, IL-36β and IL-36γ in oGVHD group at different time points(P<0.05). Compared with Non-oGVHD group, the levels of IL-36α and IL-36β at different time points were significantly increased in oGVHD group(all P<0.05).IL-36(α, β, γ)of oGVHD group was positively correlated with OSDI score, FL and CIC, while it was negatively correlated with TBUT and Schirmer test(all P<0.05).CONCLUSION: Evaluation of levels of tear IL-36(α, β, γ)can be of significance in diagnosing oGVHD after allo-HSCT. IL-36(α, β, γ)is highly expressed in the tears of oGVHD patients before the onset of ocular symptoms, and it is correlated with the ocular surface parameters.