A novel element sulfur autotrophic denitrification combined anaerobic ammonia oxidation process, reacted in CSTR, was used to investigate the sulfate production and alkalinity consumption during the whole process. The element sulfur dosage was 50 g · L⁻¹. The inoculation volume of ANAMMOX granular sludge was 100 g · L⁻¹. The agitation rate and environment reaction temperature of the CSTR were set to 120 r · min⁻¹ and 35°C ± 0.5°C, respectively. The pH of influent was maintained in range of 8. 0-8. 4. During the start-up stage of sulfur based autotrophic denitrification, the nitrogen removal loading rate could reach 0.56-0.71 kg · (m³ · d) ⁻¹ in the condition of 5.3 h hydrogen retention time and 200 mg · L⁻¹ nitrate nitrogen. After the addition of 60 mg · L⁻¹ ammonia nitrogen, Δn(SO₄²⁻):Δn(NO₃⁻) decreased from 1.21 ± 0.06 to 1.01 ± 0.10, Δ(IC): Δ(NO₃⁻-N) decreased from 0.72 ± 0.1 to 0.51 ± 0.11, and the effluent pH increased from 6.5 to 7.2. During the combined stage, the ammonia concentration of effluent was 10.1-19.2 mg · L⁻¹, and the nitrate-nitrogen removal loading rate could be maintained in range of 0.66-0.88 kg · (m³ · d)⁻¹. The Δn (NH₄⁺): Δn (NO₃⁻) ratio reached 0.43, and the NO₃⁻ removal rate was increased by 60% in the simultaneous ammonia and nitrate removal reaction under the condition of G(T) = 22-64 s⁻¹ and pH = 8.08, while improper conditions reduced the efficiency of simultaneous reaction.