Macroalgae detritus is known as an important material basis of both detritus productivity and water productivity cycle. The divergence of environmental factors, for example, dissolved oxygen concentration has significant effects on macroalgae detritus decomposition and releasing rate. To study the Sargassum vachellianum detritus degradation processes, specifically, degradation and mineral nutrition rate of nitrogen, phosphorus, silicon in dissolved oxygen concentration gradients, lab-based experiments were conducted under controlled conditions of hypoxic (1-4 mg/L) and aerobic (5-9 mg/L). The results showed that compared with hypoxic condition, the Sargassum vachellianum had higher decomposition rate (k=0.110/d, weight loss=84.699%) during the first 0-7 days, while aerobic treatment had lower decomposition rate(k=0.041/d). Similarly, hypoxic treatment had higher nitrate and nitrite release rate than aerobic treatment. Conversely, aerobic treatment released more ammonia and dissolved inorganic nitrogen (3.811 mg/g) than hypoxic treatment (1.511 mg/g), while ammonia is known as the dominant nutrient of dissolved inorganic nitrogen. For active phosphate, under different dissolved oxygen gradient, hypoxic treatment(10.143 mg/g)had 2.4-9 times contribution compared with aerobic treatment(1.091-4.777 mg/g). In a word, dissolved oxygen concentration in the waters have significant effects on Sargassum vachellianum detritus decomposition process, thus changed the nitrogen, phosphorus, silicon nutrient contribution of detritus, even the materials and energy flow in the water.