To better understand the abundance characteristics of ammonia-oxidizing microorganisms and their potential contribution to nitrate in Cunninghamia lanceolata plantation soils in Fujian Province, this studyinvestigated soils from nine representative sites. Using quantitative PCR (qPCR), we quantified the amoA gene abundance of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and Clade A of complete ammonia oxidizers (comammox Nitrospira). The results showed that Clade A had the highest gene abundance, ranging from 1.32×107 to 1.96×109 copies/g (mean: 3.27×108 copies/g), followed by AOA (9.29×105 to 3.23×109 copies/g, mean: 2.94×109 copies/g), and AOB exhibited the lowest abundance (2.24×105 to 1.53×109 copies/g, mean: 8.94×106 copies/g). AOA abundance was significantly negatively correlated with soil pH (p < 0.001), and positively correlated with the C/N ratio, NH4+-N, and available phosphorus (AP) (p < 0.001), as well as with total nitrogen (TN) (p < 0.05) and moisture content (p < 0.01). AOB abundance was only significantly positively correlated with AP (p < 0.001), while Clade A gene abundance was significantly positively correlated with AP (p < 0.001) and soil moisture (p < 0.05). Random forest and stepwise regression analyses indicated that AOA and soil pH were key factors influencing nitrate nitrogen content in C. lanceolata plantation soils, with AOA gene abundance showing a significant positive correlation with NO3--N content (p < 0.01). In conclusion, AOA plays a dominant role in the nitrification process in C. lanceolata plantation soils in Fujian Province, and soil pH indirectly regulates nitrate accumulation by affecting AOA activity.