Abstract: Calendula officinalis plants were treated with NaCl at different concentrations (0, 10, 50, 100, 200 and 300 mmol/L), while fresh and dry weights, chlorophyll content, root dehydrogenase activity, Na⁺ and K⁺ content, activity of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), MDA content, and cell membrane permeability were determined. Polyacrylamide gel electrophoresis (PAGE) of POD isoenzyme and SDS-PAGE of salt stress protein were done. Compared with the control, fresh and dry weight, chrolophyll content, SOD and POD activity initially increased but then decreased, while MDA content did the opposite. Na⁺ content and cell membrane permeability increased, while root dehydrogenase activity, K⁺ content and CAT activity decreased. Eight bands were detected through PAGE of POD isoenzyme. Only salt stress protein was induced under 10 mmol/L NaCl stress. Therefore, 10 mmol/L NaCl treatment promoted the growth of C. officinalis but the inhibitory effects on C. officinalis growth were enhanced as NaCl concentrations increased. The synthesis analysis showed that the salt tolerance threshold of Calendula officinalis was 100 mmol/L.