Four kinds of foreign and domestic micro-diets were tested for stability in water and their effects on some parameters of water quality under the same experimental conditions. It was found that, three micro-diets soaked in water settled slowly, while D4 settled more quickly. Most of the total weight loss of the four micro diets were lost during the first 5min after they were put into water. The contents of protein and fat in the four micro-diets varied significantly and fluctuated insignificantly between in 0min and in 30min after being soaked in water. After 30min, the soaking water from D1 contained the highest concentration of dissolved organic nitrogen (DON) and the lowest concentration of dissolved organic phosphorus (DOP) among four micro-diets. It was demonstrated that the four kinds of foreign and domestic micro-diets varied significantly in terms of stability in water, which had close relationship with their nutritional formula and processing techniques.