Objective:To investigate the serum level of hydrogen sulfide (H2 S ) and its influential factors in patients undergoing maintenance hemodialysis (M HD ) .Methods :Based on screening and exclusion criteria ,150 patients undergoing M HD were enrolled .Meanwhile ,17 healthy volunteers were collected as healthy controls .Venous blood samples of M HD patients were obtained before and after dialysis ,and fasting blood samples were collected from healthy controls .The levels including serum H2 S ,nitric oxide (NO) ,endothelin‐1 (ET‐1) ,and sulfhemoglobin were detected and the correlations among them were analyzed .Results:The levels of serum H2 S ,NO ,NO/ET‐1 and sulfhemoglobin in patients undergoing M HD were significantly lower than those in healthy control group before dialysis (P<0 .01) ,while ,there was no significant difference regarding ET‐1 and Vitamin B6 levels between these two groups (P>0 .05) .Before dialysis ,serum H2 S level was positively correlated with NO ,NO/ET‐1 ,sulfhemoglobin and eGFR (P<0 .01) ,while negatively correlated to serum creatinine .After dialysis ,serum H2 S level increased significantly ,while NO ,NO/ET‐1 decreased significantly .However ,the levels of ET‐1 , sulfhemoglobin and Vitamin B6 ,compared with those before dialysis ,did not change significantly after dialysis .Conclusions :Serum H2 S level in patients undergoing M HD decreases significantly and it is significantly correlated with NO ,sulfhemoglobin and renal function .Compared with that before hemodialysis ,the serum H2 S level increased significantly after hemodialysis .