With the nylon bag covered in a corn field，a field experiment was carried out to study the decomposition rule of covered soybean green manure and its effect on soil nutrient content.Results showed that the covered soybean green manure was mineralized gradually with the extension of time.The covered soybean green manure was mineralized more quickly in the first four weeks.After four weeks，the covered soybean green manure was mineralized more slowly；The covered soybean green manure in a corn field was mineralized more quickly than that in a free field.But it was insignificant between them.About542%of the covered green manure in a corn field and about 524% of the covered green manure in a free field was mineralized throughout the growth period of corn(eight weeks).However，795% of the mineralized green manure in a corn field and 771% of the mineralized green manure in a free field were released in the first four weeks after they were incorporaed into the soil.Besides，results showed that the covered soybean green manure could increase the soil nutrient content obviously.