Field experiments of winter wheat-summer maize rotation were conducted in Xushui, Hebei Province, North China Plain irrigation area, to explore the effects of dairy effluent irrigation on diversity and community structure of nirK- and nirS- type denitrifying bacteria through terminal restriction fragment length polymorphism (T-RFLP) analysis and gene sequence analysis. Five treatments were designed, including no fertilizers treatment (CK), conventional fertilization (CF) and dairy effluent irrigations with 3 fertilizer levels (T4, T5 and T11). The results showed that no significantly differences were noted in diversity indexes of nirK- and nirS- denitrifying bacteria in all treatments. And T-RFLP analysis of nirK and nirS genes addressed significant differences in community composition: both fertilizer type and amount affected the relative abundance of nirK- T-RFs significantly, especially for dominant T-RFs, and therefore affected nirK- community composition; organic and inorganic fertilizer treatments increased or decreased different nirS- T-RFs' relative abundance, resulting in significant differences in nirS- community composition. Phylogenetic analysis of nirK and nirS gene indicated that the nirK- type denitrifiers were mainly composed of Pseudomonas, Alcaligeneand and Rhizobium, nirS- type denitrifiers were mainly composed of Ralstonia and Rubrivivax. Most of these identified denitrifying bacteria were belong to families of aerobic denitrifying bacteria. A possible reason was that samples for biological analysis were taken from topsoil.