【Objective】The community structure and diversity characteristics of soil nirK-type denitrifying microorganisms in three types of primitive Pinus koraiensis forest (Picea asperata-Abies fabri-Pinus koraiensis forest, Tilia spp.-P. koraiensis forest, and Betula costata-P. koraiensis forest) were analyzed, and the key soil physicochemical factors affecting the soil nirK-type denitrifying microbial community were explored in the Liangshui National Nature Reserve of the Lesser Khingan Mountains.【Method】Soil samples of the selected three types of primitive P. koraiensis forest were collected in the Liangshui National Nature Reserve of the Lesser Khingan Mountains of Yichun City, Heilongjiang Province. Additionally, total soil microbial DNA was extracted, and variable range fragments of the nirK gene, which encodes the coding gene of nitrate reductase (a key enzyme in the denitrifying process), were amplified with PCR. The community composition and diversity characteristics of soil nirK-type denitrifying microorganisms in the different forest types of P. koraiensis were analyzed by using high-throughput sequencing and bioinformatic analysis.【Result】A total of 761 912 high-quality sequences of the 848 312 effective sequences of the nirK gene were obtained with high-throughput sequencing of 12 soil samples in the three types of primitive P. koraiensis forest, and the average length of these sequences was 320 bp. Soil nirK-type denitrifying microorganisms of the three forest types belong to bacteria and archaea.In addition there were a large number of sequences without clear classification information. The soil nirK denitrifying microorganisms identified in the three forest types belonged primarily to Proteobacteria at the Phylum level. However, the core genera included Bradyrhizobium, Rhodopseudomonas, Azospirillum and Burkholderia. Alpha diversity analysis showed that there was no significant difference in the four alpha diversity indices (Shannon, Chao1, Ace and Simpson index) of soil nirK-type denitrifying microorganisms among the three forest types. Beta diversity analysis showed that there were significant differences in the composition of soil nirK microbial communities among the three forest types (R=0.25, P=0.016). Metastats analysis showed that the significant differences in soil nirK microbial communities among the three forest types were with regards to Proteobacteria, Euryarchaeota and Bacteroidetes. Soil ammonium nitrogen and total nitrogen were the main soil physicochemical factors influencing soil nirK-type denitrifying microorganisms communities in the three forest types (P<0.05).【Conclusion】There was no significant difference in the alpha diversity index of the three primitive P. koraiensis forests (Shannon index, Simpson index, Ace index and Chao1 index), although beta diversity analysis showed that there were significant differences in the composition of the soil nirK microbial community among the three types of primitive P. koraiensis forest (R=0.25, P=0.016). Ammonium nitrogen and total nitrogen were the main soil physicochemical factors that significantly affected the soil nirK denitrifying microorganism in the three forest types.