Objective To verify the consistency of the reference intervals of thyroid hormone estimated in this investigation with the reference interval in the manual of the currently used reagent and industrial standard(WS/T 404.10-2022),and select the reference interval of thyroid hormone suitable for the healthy subjects at this hospital.Methods The indirect sampling technique was used to ret-rospectively analyze the results of thyroid hormone tests of healthy subjects in the Clinical Testing Center of Suzhou Dushu Lake Hospi-tal from December 2022 to August 2023.Nonparametric method was used to estimate thyroid hormone P2.5-P97.5 reference intervals and 95％confidence intervals of the testing subjects with different genders and ages,and to explore the significant differences in the data distribution among different gender and age groups.The differences were compared with the reference intervals recommended by the in-dustrial standard(WS/T 404.10-2022)and Roche reagent specification.Results There were significant differences in TSH,FT3,FT4 and TT3 between sexes(P＜0.001,Z＞Z*),but there was no significant difference in TT4 between sexes(P=0.998,Z＜Z*).In terms of TSH levels,the women were divided into 20 to 60-year-old group(reference interval:0.62-6.40 mIU/L)and≥61-year-old group(reference interval:0.85-7.47 mIU/L).There was significant difference between the 2 groups(P＜0.001),but there was no sig-nificant difference of TSH levels among the male groups with different age(reference interval:0.79-5.64 mIU/L).In terms of FT3 lev-els,the males were divided into 20 to 40-year-old group(reference interval:4.37-6.36 pmol/L)and ≥41-year-old group(reference interval:4.02-6.34 pmol/L).There was significant difference between the 2 groups(P＜0.001),but there was no significant difference in the female among various age groups(reference interval:3.44-5.63 pmol/L).In terms of FT4 level,the males were divided into 20 to 50-year-old group(reference interval:13.7-21.4 pmol/L)and ≥51-year-old group(reference interval:12.0-20.4 pmol/L),and the females were divided into 20 to 50-year-old group(reference interval:12.5-20.25 pmol/L)and≥51-year-old group(reference interval:11.34-19.18 pmol/L).There was all significant difference between various age groups in both male and female(P＜0.001).In terms of TT3 level,no difference was found between male and female regardless of age(male[reference interval:1.18-2.18 nmol/L]and female[reference interval:1.10-2.23 nmol/L]).In terms of TT4 level,there was no significant difference between sex and age(reference interval:64.1-127 nmol/L).There was no significant difference between the reference interval recommended by Roche reagent manual and the laboratory estimated FT4 reference interval,but there were significant differences in reference interval of TSH,FT3,TT3 and TT4.There was no significant difference between the industrial standard recommended reference interval and the laboratory estimated reference interval.Conclusion There were differences of TSH,FT3 and FT4 levels for gender and age,but no differences of TT4 levels for sex and age.There was gender difference of TT3 levels but no differences for age.The estimated reference interval verified by the laboratory was consistent with the industrial standard recommendation of WS/T 404.10-2022,but it was differ-ent from the recommendation of current Roche reagent manual.