Objective：To explore the prevalence and clinical features of hyponatremia in tuberculous meningitis（TBM）. Methods：One hundred and fifteen patients diagnosed with TBM in the hospital from January 2014 to October 2016 were enrolled. General information and clinical data were collected. Clinical features of TBM with and without hyponatremia were compared.Occurence of hyponatremia in TBM was calculated.Clinical features of patients with and without hyponatremia were compared. Results：In our study，70.4% patients were with hyponatremia. Compared with normonatremic counterparts，besides lower serum sodium and plasma osmotic pressure，pa－tients with hyponatremia also tended to have lower serum creatinine[54.5（45.2，68.0） μmmol/L vs. 64.0（54.5，75.7） μmmol/L，P=0.004]，blood uric acid[164.0（123.5，218.2） μmmol/L vs. 229.5（178.5，327.0） μmmol/L，P<0.001]，glucose[2.0（1.7，3.0） mmol/L vs. 3.0（2.0，4.0） mmol/L，P=0.002] and chloride content[112.0（104.0，116.0） mmol/L vs.120.0（116.2，125.7） mmol/L，P<0.001] in cerebrospinal fluid. Both temperature[（37.4±1.0）℃ vs. （36.7±0.7） ℃，P=0.002] and protein content in cerebrospinal fluid[2.0（1.2，3.0） g/L vs. 1.0（0.8，2.1） g/L，P=0.003] were higher in the hyponatremic patients. There was no significant difference in gender and age between this two groups. According to the analysis of the reason for TBM with hyponatremia，65.4% patients with syndrome of inappropriate antidiuretic hormone secretion（SIADH）. Compared with the patients with hyponatremia for other reason，patients with SIADH had lower serum sodium，plasma osmotic pressure，blood uric acid，chloride content in cerebrospinal fluid，while the cerebrospinal fluid pressure was higher. In patients with SIADH，as high as 90.6% of them missed the diagnosis. Conclusion：According to this study，the incidence of TBM with hyponatremia is high. SIADH is an important cause of TBM with hyponatremia.