In order to improve the content of polyphenols in the liquid fermentation product of Morchella esculenta and investigate the antioxidant activity of the fermentation broth， the fermentation medium with the highest polyphenol content in M. esculenta fermentation broth was obtained by optimizing the composition and addition of the liquid fermentation medium， using single-factor and response surface experiments: 0.5% potato starch， 4.0% soy protein， and 0.3% potassium phosphate. Under these conditions， the theoretical polyphenol content obtained by software analysis is 1.02 mg/mL. After that， the antioxidant activity of the fermentation broth was evaluated by in-vitro antioxidant assay， and the IC50 value of the fermentation broth for DPPH scavenging rate was 1.83 mg/mL， ABTS scavenging rate was 4.81 mg/mL， hydroxyl radical scavenging rate was 0.78 mg/mL， and the FRAP value for the reduction of Fe3+ was 0.75 mmol/L at the fermentation broth lyophilized powder concentration of 15 mg/mL. The fermentation broth had a strong free radical scavenging effect as well as reduction ability. The results of the study increase the possibility for the development of liquid fermentation products of M. esculenta.