Abstract: In this study, the selenium ore bodies already delineated in Shuang'an, Ziyang, Ankang, were taken as the research subject, with 20 mg/kg and 60 mg/kg set as the lower and upper cut-off grades, respectively. The effects of different cut-off grades including 20, 30, 40, 50, and 60 mg/kg on ore body continuity, total selenium-rich ore quantity, and selenium reserves were systematically examined. Based on the break-even method, the intrinsic relationships among cut-off grade, mining cost, total sales, and sales revenue were analyzed. Following the principle of benefit maximization, 43 mg/kg was finally selected as the optimal selenium cut-off grade for selenium-rich fertilizer development.The corresponding reserves are 16.3421 million tons, with sales revenue of 65.368 billion CNY and a maximum corporate profit of 54.746 billion CNY. This study indicates that developing selenium-rich fertilizers for soil improvement has broad market prospects and can generate substantial economic benefits, effectively support the construction of "China Selenium Valley Ecological Ankang". Following the principle of benefit maximization, 43 mg/kg was finally selected as the optimal cut-off grade for selenium-rich fertilizer development. The corresponding reserves are 16.3421 million tons, with sales revenue of 65.368 billion CNY and a maximum corporate profit of 54.746 billion CNY. This study indicates that developing selenium-rich fertilizers for soil improvement has broad market prospects and can generate substantial economic benefits, effectively supporting the construction of "China Selenium Valley · Ecological Ankang".