To study the effects of superphosphate (SP) and nitrification inhibitor dicyandiamide (DCD) on NH_3, N_2O and CH_4 emissions, an experiment of straw and sludge co-composting for 34 days was carried out. This research used 60 L sealed fermenter as composting reactor, raw sludge as basic composting material, corn stalk as porous material and set four composting treatments. The control check (CK) was the co-composting of straw and sludge without any additives. Other three treatments, SP3.5 treatment was only added with 3.5% superphosphate, SD3.5 and SD5.0 treatments were added with 0.1% dicyandiamide (DCD) besides the basic materials, with 3.5% superphosphate (SP3.5) and 5% superphosphate (SP5.0) , respectively, based on the wet weight of the materials. The results indicated that, during 34 days test, the combination use of SP and DCD additives can promote the decomposition of compost and improve the stability and maturity. The highest temperature of all treatments was greater than 70℃. The temperature higher than 50 ℃ of CK, SP3.5, SD3.5 and SD5.0 treatments lasted for 4, 4, 4 and 2 d respectively, which met the compost sanitation requirements. The germination indices of CK, SP3.5, SD3.5 and SD5.0 treatments were 103.21%7.38%, 97.4%4.50%, 120.31%3.15% and 111.00%2.70%, respectively. Statistical analysis data showed the germination indices of SD3.5 and SD 5.0 were significantly higher than those of other two treatments (P<0.05), which were promoted by 17.1% and 7.8% compared to CK. E4/E6 values of CK, SP3.5, SD3.5 and SD 5.0 treatments were 2.090.36, 2.200.26, 1.880.10 and 1.790.04, respectively. The E4/E6 values of SD3.5 and SD 5.0 were decreased by10.0% and 14.4 % compared to CK. The EC value of all treatments used superphosphate and dicyandiamide were below 4 mS/cm, which could be biologically non-toxic. The total organic carbon losses of CK, SP3.5, SD3.5 and SD 5.0 treatments were 55.95%, 50.26%, 49.66% and 49.64%, respectively. The total organic carbon losses of treatments used additives were decreased by 11.2%-11.3%. Meanwhile, the total nitrogen losses of CK, SP3.5, SD3.5 and SD 5.0 treatments were 37.08%, 28.22%, 26.16% and 24.00%, respectively. The total nitrogen losses of treatments used additives were decreased by 10.92%-13.08%. The results showed that the CK had the peak value of gases emission among all treatments. NH_3 and CH_4 mainly occurred in the mesophilic and thermophilic phase of composting, process, while N_2O occurred predominantly in the later period of composting. While combination use of superphosphate and dicyandiamide, the peak values of CH_4, N_2O and NH_3 emission were decreased. Besides, the cumulative emissions of CH_4, N_2O and NH_3 also were decreased by 69.6%-82.6%, 88.1%-92.9% and 48.5%-52.8%, respectively. The global warming potentials of CH_4 and N_2O, on a 100-year time frame, were 25 and 298 times higher than that of CO_2, respectively. The global warming potential value of CK, SP3.5, SD3.5 and SD5.0 were 170.11, 109.11, 58.47 and 42.94 kg/t. The combination use of superphosphate and dicyandiamide additives significantly mitigated total GHG emissions. The total greenhouse effects were decreased by 65.6%-74.8%.