A series of hazes occurred over the North China plain in January 2013. In this paper, the authors analyzed the morphologies, elemental compositions and sulfation characteristics of the individual aerosol particles collected in Beijing, Tianjin and Tangshan cities in January 2013 by Transmission Electron Microscopy(TEM) coupled with Energy Dispersed X-ray Spectrometry(EDX). The results showed that the individual aerosol particles could be subdivided into mineral particles, sulfate particles, metal oxide particles, soot aggregates, organic particles, and fly ash. A small amount of sea salt particles was found only in the Tianjin samples. According to element compositions, the individual particles were dominated by Si(31.0%), Ca(18.3%), Fe(14.1%) and Cl(12.2%) in the sunny days, and by S(47.4%), Si(21.1%) and Fe(13.4%) in the haze days. The high-S particles were commonly associated with higher values of Ca and K, indicating that alkaline minerals could be buffered against the acid mist. An analysis of sulfation characteristics showed that the S-bearing particles were more common in haze days, and that the S/Ca ratio was higher(>0.8) in the hazy days, indicating that the haze day is favorable for secondary reactions and formation of the S-rich particles.