For determining changes in soil microbial transformation of nitrogen in a crop rhizosphere under ozone(O₃)stress, using ozone treatments in OTCs (open top chambers), the effects of increase atmospheric surface level O₃ contents on soil microbial transformation of nitrogen in winter wheat (Triticum aestivum)rhizosphere was investigated, during the growing/development (G/D) periods including reviving, jointing, booting, heading, filing and maturing stages. Four independent experiments were performed in four years, each for one year,using six OTCs. The chambers were equivalent, but two were fed with air while the other four with ozone at different concentration, in that two chambers with 100 nL/L and the other two with 150 nL/L. Winter wheat were grown to all life stage in OTCs. From reviving to mature stages, the plants were treated for 8 h (8:00-16:00) in every sunny day with different dose of O₃, respectively. Soil microbial biomass N, amount of ammonium-oxidizing bacteria and denitrifying bacteria, soil nitrifying and denitrifying capacity were measured. Each treatment was assayed in triplicate. The data were initially compared by analysis of variance and differences between means were detected using the Duncans Multiple Range Tests. Values of P < 0.05 indicated significance. Quite similar results were obtained during the four years' experiments, suggesting that as a G/D stage is progressing, soil microbial biomass N, amount of ammonium-oxidizing bacteria and soil nitrifying capacity increased firstly but consequently declined. Under increased O₃ stress, either soil microbial biomass N, or amount of ammonium-oxidizing bacteria or nitrifying capacity were found dropped. Their differences compare to control were significant (P < 0.05). With the increased of O₃ dosage, the inhibition effects were found increasing. Inhibition rate of soil microbial biomass nitrogen, amount of ammonium-oxidizing bacteria and nitrifying capacity on wheat growth stages in the fourth years were significantly higher than those of the first year. The number of denitrifying bacteria was found to be no significant change in the earlier stages, but increased two orders of magnitude in the maturing stage. In maturity stage, the quantity of denitrifying bacteria was significantly improved by O₃.Four years test showed the same change trend. No obvious influence of O₃ on soil denitrifying capacity was found under short time ozone fumigation, but significantly increased during the later three growing seasons. Taking together,the elevated O₃ concentration in atmospheric surface layer, impinges on the features of soil microbial transformation of nitrogen. O₃ stresses can reduce soil microbial biomass N, amount of ammonium-oxidizing bacteria and nitrifying capacity. Enhance O₃ irradiation and prolong fumigation time the Inhibition efficiency was up-regulated. When the cumulant of O₃ dose and fumigation time reached a certain threshold, the number of denitrifying bacteria and denitrifying capacity rose up, meanwhile soil N₂O emission risk was heighten. The effects on nitrogen microbial transformation were found to relate to (G/D) periods of winter wheat, dose of O₃ and the exposure time. The different forms of nitrogen have different O₃-sensitive, indicating that the threshold of subjected to O₃, the responses time to O₃ stress and the variation scope are different.