[Objective] In order to provide scientific basis for effective control and ecological management of the invasive plants in China, the effects of invasive plants on soil nitrogen and metabolic enzyme activities were explored.[Methods] Field control experiments were conducted to study the soil nitrogen contents, enzyme activities and microbial characteristics of four exotic invasive plants (Lepidium apetalum, Ageratina Adenophora, Conyza canadensis, Flaveria bidentis) and native Petunia hybrida (control plant) for five consecutive years.[Results] ① Plant invasion reduced the nitrogen contents in leaves, stems and roots, which showed as follows:Petunia hybrida > Ageratina Adenophora > Lepidium apetalum > Flaveria bidentis > Conyza canadensis. ② Plant invasion reduced soil nitrogen contents (total nitrogen, mtrate nitrogen, and ammonium nitrogen), which showed as follows:Petunia hybrida > Ageratina Adenophora > Lepidium apetalum > Conyza canadensis > Flaveria bidentis. While the soil pH value revealed an opposite trend showing that plant invasion had increased pH value. ③ The activities of soil protease, urease, and nitrate reductase of different plants showed the same trends:Petunia hybrida > Ageratina Adenophora > Lepidium apetalum > Conyza canadensis > Flaveria bidentis(p<0.05). ④ The soil microbial biomass carbon and nitrogen of different invasion plants also showed the same trend:Petunia hybrida > Ageratina Adenophora > Lepidium apetalum > Conyza canadensis > Flaveria bidentis. Ageratina Adenophora and Lepidium apetalum were significantly higher than Conyza canadensis and Flaveria bidentis (p<0.05). Soil microbial biomass phosphorus showed as:Petunia hybrida > Ageratina Adenophora > Lepidium apetalum > Conyza canadensis > Flaveria bidentis. ⑤ Principal component analysis indicated that soil nitrate nitrogen, ammonium nitrogen and pH value were the main influencing factors of invasive plants.[Conclusions] Different invasive plants could change soil nitrogen form, enzyme activities and microbial characteristics, and the stronger nitrogen assimilation ability and the accelerated soil nitrogen could be regarded as one of the important mechanisms for successful plant invasion.