【Abstract】Objective To examine the changes of serum thyroid hormones and their effect on survival in patients undergoing maintenance hemodialysis dialysis (MHD). Methods Baseline data including demographic information, thyroid hormone tests, and clinical biochemistry were collected from MHD patients treated in Peking University Third Hospital in November 2011 and a fivEyear follow-up was then performed. The patients were divided into three groups: euthyroid, low triiodothyronine (T3) syndrome, and hypothyroidism. OnEway ANOVA was used to compare the differences among groups. Multivariate regression analysis was performed to examine the affecting factors for serum free T3 (FT3). Cox proportional hazards modeling was used to analyze the association between serum thyroid hormones and all-cause mortality. Results A total of 121 patients were included in this study, of whom 78 (64.50%) had low T3 syndrome and 15 (12.40%) had hypothyroidism. In patients in low T3 syndrome group or hypothyroidism group, the proportion of female (χ2=10.082, P=0.006) and older age (F=4.899, P=0.009) were higher but body weight (F=4.129, P=0.019) and serum prealbumin (F=6.233, P=0.003) were lower, as compared with those in euthyroid group. Multivariate regression analysis showed that serum CRP and prealbumin were the independent influence factors on serum FT3 level (β =-0.266, P=0.004; β=0.250, P=0.022). COX regression analysis showed that serum FT3 was an independent risk factor for death in MHD patients (HR 0.343, 95% CI 0.130～0.906; P=0.031) but TSH was not the risk factor (HR 0.997, 95%CI 0.969～1.026; P=0.831) after adjusting sex, age, diabetes mellitus, dialysis vintage and hemoglobin. Conclusions Our study indicates that low T3 syndrome is a dominant modality of thyroid dysfunction, and serum FT3 but not TSH can independently predict the all- cause mortality in MHD patients.