The association of 24 h urinary Na and potassium excretion with the risk of the metabolic syndrome (MetS) has not been studied in China. The aim of the present study was to examine this association by analysing the data from 1906 study participants living in north China. To this end, 24 h urine samples were collected. Of the 1906 participants, 471 (24·7 %) had the MetS. The mean urinary Na and K excretion was 228·7 and 40·8 mmol/d, respectively. After multivariate adjustment, the odds of the MetS significantly increased across the increasing tertiles of urinary Na excretion (1·00, 1·40 and 1·54, respectively). For the components of the MetS, the odds of central obesity, elevated blood pressure and elevated TAG, but not the odds of low HDL-cholesterol and elevated fasting glucose, significantly increased with the successive tertiles of urinary Na excretion. Furthermore, for every 100 mmol/d increase in urinary Na excretion, the odds of the MetS, central obesity, elevated blood pressure and elevated TAG was significantly increased by 29, 63, 22 and 21 %, respectively. However, urinary K excretion was not significantly associated with the risk of the MetS. These findings suggest that high Na intake might be an important risk factor for the MetS in Chinese adults.