Net bags were employed to research characteristics of decomposing and nutrients releasing of cassava stalk under different ways returned to field.The results showed that the decomposing speed of cassava stalk was fast during 30 to 60 days under different ways returned to field.Under covered with soil,covered with soil and plastic film and covered with plastic film only,the accumulated decay rate was 69.9%,80.8% and 73.8% respectively at the 240th day,and was ranked as:covered with soil and plastic film >covered with plastic film only>covered with soil.Releasing speed of nutrients of cassava stalk ranked as:potassium > phosphorus >nitrogen≈carbon.The accumulated releasing rates of carbon,nitrogen,phosphorus and potassium were 69.9%~80.8%,78.1%~94.2%,87.3%~93.5% and 97.4%~98.5% respectively at 240th day.Considering both the nutrients releasing and carbon nitrogen ratio,it was suggested that the content of potassic fertilizer in base manure should be reduced and nitrogen fertilizer could be increased according to growth of cassava.The way of covered with soil and plastic film when returned cassava stalk to field could be the best choice.