Secondary organic aerosol (SOA) is from the oxidation of atmospheric volatile organic compounds (VOCs), and accounts for a large fraction of ambient fine particles. SOA can directly and indirectly affect the solar radiation forcing, so it has great impact on global climate and regional air quality. Adverse effects of SOA on human health have also been found these years. Thus SOA study has become one of the hottest topics of atmospheric chemistry. However, due to the complexity of SOA and the limit of technology, our understanding about SOA's composition, sources and formation mechanism is very limited. The major approaches of SOA study include: laboratory simulation, modeling simulation and field measurement. This paper reviews the SOA studies basing on field measurement. The development of SOA measurement depends on the development of technology. Early studies can only measure limited polar compounds of ambient particles. Rough estimations have been made by using relatively well developed approaches, e.g. receptor model and non-biomass burning water soluble organic compounds. Tracer-yield method combines laboratory and ambient studies, and is so far the only approach that can estimate SOA from specific precursors. Development of on-line detection technique encourages new approaches to study SOA, e.g. EC (elemental carbon)/CO (carbon monoxide) tracer method, and AMS-PMF approach. The combination of AMS and organic tracer technique is probably the important direction of SOA study in the future.