Abstract: The snap bean purple mutant ‘pv-pur’ and its wild type ‘A18-1’ were used as the experimental materials, using hydroponic culture, the effect of alkali stress on the purple mutant of snap bean was investigated with 0 mmol·L^-1 NaHCO₃ as the control group（CK） and 50 mmol·L^-1 NaHCO₃ added to the treatment group, the agronomic traits, photosynthetic parameters, MDA（malondialdehyde） content and antioxidant enzyme activity of snap bean seedlings were determined, in order to investigate the response ability of the artificially mutated snap bean purple mutant to alkali stress.The results showed that the reduction of agronomic trait indexes was significantly lower in ‘pv-pur’ than of in ‘A18-1’,the inhibition of photosynthesis and respiration was significantly higher than that in ‘A18-1’,MDA content was significantly higher than that of ‘A18-1’,and antioxidant enzyme activity was significantly lower than that of ‘A18-1’.In conclusion, ‘pv-pur’ was damaged by stress to a greater extent under alkali treatment compared with the wild type, which may be due to the damage caused by radiation to the plant during mutagenesis.‘pv-pur’ was an alkali-sensitive mutant and alkaline soil should be avoided in cultivation.