In order to excavate high-efficiency nitrogen-removing strains from high ammonia nitrogen breeding wastewater, a heterotrophic nitrifying strain ZF1-1 with high denitrification efficiency was isolated from the natural aeration tank sewage of pig manure-water using enrichment culture method. Based on morphological analysis, 16S rRNA gene sequence alignment and phylogenetic tree construction, strain ZF1-1 was identified as Bacillus siamensis. The denitrification characteristics of ZF1-1 showed that, in an artificial wastewater culture medium using ammonium sulfate as the only nitrogen source, the strain had a conversion rate of 77.55% to ammonia nitrogen, a total nitrogen removal rate of 21% and no nitrate and nitrite (intermediate products) accumulation when the inoculum amount was 1% at 30 ℃, 180 r/min for 72 h. The optimum carbon source for nitrifying ammonia nitrogen of strain ZF1-1 is mannitol, and the optimum carbon-nitrogen ratio is 20. Increasing initial concentration of ammonia nitrogen resulted in decreasing of ammonia nitrogen conversion rate under the same experimental conditions and incubation time. The highest conversion rate of ammonia nitrogen is 93.46% when the initial ammonia nitrogen concentration reaches 100 mg/L. Fe2+, Fe3+ and Mg2+ can significantly improve the conversion rate of ammonia nitrogen for of 98.66%, 93.48% and 86.47% respectively. Subsequently strain ZF1-1 was applied to remove nitrogen (1277.41 mg/L) from pig manure-water with high ammonia nitrogen concentration. The results reveal that strain ZF1-1 exhibit a satisfactory treatment effect, can reduce the ammonia nitrogen and total nitrogen concentrations to 37.50% and 22.22% respectively in the wastewater. Therefore, the strain ZF1-1 has good application potential for nitrogen removal in high ammonia nitrogen polluted wastewater from livestock and poultry breeding.