Quantitative information on mass concentrations and other characteristics, such as spatial distribution, seasonal variation, indoor/outdoor (I/O) ratio correlations and sources, of indoor and outdoor PM2.5 and elemental components in Guangzhou City were provided. Mass concentration of PM2.5 and elemental components was determined by standard weight method and by proton-induced X-ray emission (PIXE) method. 18 elements were detected, the results showed positive results. Average indoor and outdoor PM2.5 concentrations in nine sites were in the range of 67.7 and 74.5 μg/m3 for summer period, and 109.9-123.7 μg/m3 for winter period, respectively. The sum of indoor and outdoor 18 elements average concentrations were 5362.6-5533.4 ng/m3 for summer period, and 8416.8-8900.6 ng/m3 for winter period, respectively. Average concentrations of PM2.5 and element components showed obvious spatial characteristic, that the concentrations in roadside area and in industrial plant area were higher than those in generic urban area. An obvious seasonal variation characteristic was found for PM2.5 and elemental components, that the concentrations in winter were higher than that in summer. The I/O ratio of PM2.5 and some elemental components presented larger than 1 sometimes. According to indoor/outdoor correlation of PM2.5 and elemental concentrations, it was found that there were often good relationships between indoor and outdoor concentrations. Enrichment factors were calculated to evaluate anthropogenic versus natural elements sources.