Abstract: To characterize the aerosol pollution of Hong Kong, the atmospheric PM₁₀ chemical compositions at five stations in 2010-2011 were analyzed. Backward trajectories were calculated and classified using a Lagrangian dispersion and transport model (HYSPLIT) to identify the origin of air masses arriving at Hong Kong. The results suggested PM₁₀ in Hong Kong was mainly formed as nss-SO₄^2-, NH₄⁺, NO₃^-, organic matter, sea-salt and mineral dust. Second inorganic ions (nss-SO₄^2-, NH₄⁺ and NO₃^-) were the biggest contributor to PM₁₀, accounting for 33.0% in PM₁₀. Four major air mass groups which are from East China, Central China, East China Sea and South China Sea, were identified. The differences of PM₁₀ and the chemical compositions among the five stations were mainly affected by air mass sources. Air mass transport from mainland was a major contributor to the aerosol pollution in Hong Kong.