Abstract: Abstract: Returning crop straw into the soils is one of the important steps towards sustaining and improving soil fertility. As a large agricultural country, China has more than 700 million tons crop straw engendered annually. Various practices of returning straw, such as chopping, mulching and deep burying, have been invented and used widely in rural areas. However, low yield of crop always occurs in the next season if excessive amount of straw has been returned, which even leads to plant disease and insect pest. Further, environmental issues increase due to a lot of crop straw returning to the field. Thus, effective techniques for returning crop straw and increasing soil productivity should be developed to cope with these challenges. As an innovative way of returning straw, we granulated the maize straw with the help of a straw granulated machine and then returned them into the soils. To evaluate the effects of granulated straw and chopped straw (standing for the control) on straw decomposition, nutrient release and soil respiration, a successive laboratory incubation experiment was conducted at Chinese Academy of Agricultural Sciences in Beijing, China. After granulating, the bulk density of maize straw was 254.09 kg/m3, 4.8 times the value of the control. As a result, the rates of straw returning increased considerably in a unit soil. In this experiment, both the granulated and chopped straw were put in several nylon bags and then buried into soils at a depth of 15 cm. In the course of the experiments, they were sampled randomly and determined. In the earlier 60 d, the mean decomposition rate of granulated straw was 31.68% higher than that of the control. After 300 d, the cumulative decomposition rate of granulated straw was 80.81%, 8.7percentage points higher than that of the control. Based on the regression analysis between nutrient releasing rate and decomposition time for different pre-treatments of maize straw, the granulated straw treatment was 30 or 14 d earlier than the chopped straw treatment when they half or completely decayed, respectively. In addition, the granulated straw treatment significantly increased the nutrient release rate throughout the entire incubation period, especially in the early 60 d. After 300 d, the granulated straw treatment increased the cumulative release amount of C (carbon) and N (nitrogen) by 11.0 percentage points and 13.2 percentage points compared to the corresponding level of the control, respectively. However, no significant differences were found for the cumulative release amount of P (phosphorus) and K (potassium) between the granulated and chopped straw treatment. According to the results of data fitting, the time of more than 50% releasing nutrient for the granulated straw treatment was 15-125 d earlier than the control; in contrast, it was 9 d earlier than the control when its nutrient was released completely. In addition, the mean value of soil respiration rate for the granulated straw treatment was 18.03% greater than the control in the earlier 260 d. In conclusion, maize straw that was granulated before returning into soils can fast and effectively improve soil fertility; and thus, it is worthy widely applying in agricultural production.