Abstract: A 60-day incubation experiment was conducted to study the effects of nitrogen fertilization (N), rice straw amendment (R), and their combination (RN) on the changes of soil microbial biomass and soil functions (basal respiration, substrateinduced respiration, and straw decomposition) after heat stress (40 ℃ for 18 h). Heat stress tended to promote the soil microbial biomass and soil functions, but the effects were weak and transient. Either with or without heating, treatment R and especially RN could greatly stimulate soil microbial biomass, basal respiration, substrate-induced respiration and straw decomposition, as compared to no straw amendment and with nitrogen fertilization alone, but the parameters in treatment N  had less change, and even, presented a decreasing trend. It was suggested that straw amendment and its combination with nitrogen fertilization could improve soil functions in natural conditions or after environmental stress.