Abstract: To promote scientific progress and optimize the utilization of natural plant resources that rich in selenium, the study selected selenium-rich Hibiscus manihot L. as the research object, using the HG-AFS to detect the selenium content in different plant organ samples, ultrasound assisted ethanol extraction of selenium containing organic active components from sunflower flowers, and obtaining the optimal extraction process by response surface methodology. At the same time, conducting antioxidant activity research on selenium containing extracts. The results showed that the total Se concentrations in different organs of Hibiscus manihot L., from highest to lowest were found in the leaves, fruits, flowers, roots, and stems, with concentrations of 21.99, 14.29, 12.93, 10.90, and 10.23 mg/kg, respectively. The RSM optimization results indicated that the ideal conditions for the extraction parameters were as follows: Extraction temperature of 40 ℃, solid-liquid ratio of 1:60, extraction time of 40 minutes, ultrasonic power of 350 W, ethanol concentration of 50% (V/V), under one-time extraction. For the optimal conditions, the selenium extraction rate was 36.65%±0.65%. The DPPH antioxidant activity analysis showed a half-inhibitory concentration (IC₅₀) value of 0.048 mg/mL (with a Se concentration of 0.79 μg/mL), the hydroxyl radical scavenging analysis showed that the maximum clearance rate was 97% when the extracts concentration was 8 mg/mL, and the IC₅₀ was 0.56 mg/mL. The reducing power analysis showed that the reducing power of the extracts increases with the increase of the concentration, indicating that the extracts possess a good antioxidant capacity. The present study would provide empirical evidence to support the efficient use of selenium-rich Hibiscus manihot L. and the extraction of selenium-rich agricultural by-products.