Abstract. Recent studies have revealed that halogen radicals (Cl, Br, and I) significantly influence atmospheric oxidation capacity, affecting O3 formation or destruction. However, understanding of halogen chemistries remains limited. To better investigate atmospheric halogen chemistries, we incorporated halogen processes into the Community Multi-scale Air Quality (CMAQ) model: (i) emissions of Cl2, HCl, Br2, and HBr from anthropogenic sources, and Br2, I2, HOI, and halocarbons from natural sources; and (ii) 177 multi-phase halogen reactions. After developing the model, we examined its performance against observed data. The results demonstrated significant improvements in simulating observed nitryl chloride (ClNO2) mixing ratios at supersites. The index of agreement (IOA) improved from 0.41 to 0.66, and the mean bias (MB) decreased from -159.36 ppt to -25.07 ppt. These improvements were driven by four atmospheric key reactions: (i) ClO + ClO → Cl2; (ii) HOBr + Cl- → BrCl; (iii) different parameterization of γN2O5; and (iv) 2NO2 + Cl- → ClNO + NO3-. We then examined the net Ox production rate (P(Ox)), which increased from 3.08 ppb/h to 3.33 ppb/h on land and decreased from 0.21 ppb/h to 0.07 ppb/h over ocean in the presence of halogen radicals. Further analysis of the impacts of halogen processes on key atmospheric species revealed that levels of OH, HCHO, and NOx increased by ~0.007 ppt (5.5 %), ~0.03 ppb (1.6 %), and ~0.29 ppb (2.9 %), respectively, while levels of HO2 and VOCs decreased by ~0.45 ppt (5.3 %) and ~0.71 ppb (5.9 %), respectively.