According to the free amino acid content including proline content after NaCl treatment, 21 free amino acids were analyzed. Glutamine content was the highest after 0.25% and 2.0% NaCl treatment and in the control, while arginine content was the highest after 0.5% and 1.0% NaCl treatment. The total free amino acid in Apocynum lancifolium followed the order 2.0% NaCl treatment > 0.5% NaCl treatment > 0.25% NaCl treatment > 1.0% NaCl treatment > control; in particular, the total free amino acid content after 2.0% NaCl treatment (7428.94 mg/kg) was about 3.4 times higher than that in the control (2218.94 mg/kg). The proline content after 2.0% NaCl treatment was 47.49 mg/kg, while it was the lowest in the control. Antioxidant content, such as flavonoid CE (catechin equivalent) and total polyphenol GAE (gallic acid equivalent), and antioxidant activity AAE (ascorbic acid equivalent) were the highest after 0.25% NaCl treatment (29034.17 mg CE/kg, 24607.68 mg GAE/kg, and 39231.67 mg AAE/kg, respectively).