A naphthalimide-azide based colorimetric and ratiometric fluorescent probe, NAP-1, has been developed for the selective and sensitive detection of hydrogen sulphide. Advantages of the probe NAP-1 include a low detection limit (110 nM), good selectivity, high sensitivity and excellent photostability. A linear relationship between the emission intensity ratios and sulphide concentrations was observed in PBS buffer and bovine serum, respectively. Our probe facilitates ratiometric determination and imaging of endogenous H2S in living cells. Furthermore, this probe was successfully applied to the measurement of endogenous sulphide in human plasma and mouse hippocampus. A significant reduction in sulphide levels and CBS mRNA expression was observed in the hippocampus of mouse models of lipopolysaccharide-induced neuroinflammation-related diseases, suggesting that decreased levels of endogenous H2S might be involved in the pathogenesis of neuroinflammation-related neurodegenerative diseases.