With the increase of greenhouse gases emission in urban regions, urban carbon cycle plays a more and more important role in global carbon cycle. To estimate urban carbon emission and carbon storage is crucial for understanding urban carbon cycle. By using China's statistics data and the results from recent publications, this paper estimated the organic carbon storage in China's urban built-up areas in 1997-2006. From 1997 to 2006, the total organic carbon storage in the urban built-up areas increased from 0.13-0.19 Pg C (averagely 0.16 Pg C) to 0.28-0.41 Pg C (averagely 0.34 Pg C), and the organic carbon density increased from 9.86-14.03 kg C x m(-2) (averagely 11.95 kg C x m(-2)) to 10.54-15.54 kg C x m(-2) (averagely 13.04 kg C x m(-2)). The total organic carbon storage in the urban built-up areas was mainly contributed by soils (78% in 1997 and 73% in 2006), followed by buildings (12% in 1997 and 16% in 2006) and green spaces (9% in 1997 and 10% in 2006), while the carbon storage in resident bodies only accounted for less than 1%, which could be neglected.