The effects of spent mushroom substrate (SMS) and sucrose (S) amendment on emissions of nitrogenous gas (mainly NH3 and N2O) and end products quality of sewage sludge (SS) composting were evaluated. Five treatments were composted for 20 days in laboratory-scale using SS with different dosages of SMS and S, without additive amended treatment used as control. The results indicated that SMS amendments especially combination with S promoted dehydrogenase activity, CO2 production, organic matter degradation and humification in the composting, and maturity indices of composting also showed that the 30% SMS + 2% S treatment could be much more appropriate to improve the composting process, such as total Kjeldahl nitrogen, nitrification index, humic acids/fulvic acids ratio and germination index, while the emissions of NH3 and N2O were reduced by 34.1% and 86.2%, respectively. These results shown that the moderate addition of SMS and S could improve the compost maturity and reduce nitrogenous gas emission.