Abstract: To explore the process of extraction and antioxidant activity of products from marine sponge, three influencing factors, ultrasonic temperature, ultrasonic time, and ultrasonic power were investigated respectively taking DPPH radicals scavenging rate of ethanol extracts from H. erectus as the response value, and the optimal ultrasonic-assisted extraction process was determined by Box-Behnken design. The extract obtained from H. erectus by the best ultrasonic-assisted process was detected for antioxidant activity, which included the scavenging effect on DPPH radicals, ABTS⁺• and •OH. The effects of the extract on viability of oxidative damage L02 cells and content of intracellular ROS were detected by constructing a cell model of H₂O₂ induced oxidative damage. The results showed that the optimized process conditions were as follows: Ultrasonic temperature was 57 ℃, ultrasonic time was 60 min, and ultrasonic power was 490 W. Under these conditions, the DPPH scavenging rate of the extract was 61.98%±1.52%, which agreed well with the predicted value of 62.16%. The extract showed good scavenging effects on DPPH radical, ABTS⁺• and •OH. The cell viability of treated groups was significantly higher than that of the model group (P<0.05), and the intensity of intracellular ROS fluorescence was significantly lower than that of the model group (P<0.01). In general, the product from H. erectus had a wide range of antioxidant activity, and it had a protective effect on H₂O₂ induced oxidative damage in L02 cells. This study provides theoretical support for the research and development of antioxidant food additives.