Abstract: All balloon floating information from 120 Chinese upper-air meteorology cal sounding stations are utilized to analyze the temporal and spatial floating characteristics on standard constant pressure surfaces integrated with the NCEP reanalysis data. The data of January, April, July and October of 2004 with the focus on 100, 500 and 925 hPa are chosen to represent winter, spring, summer and autumn, respectively. The results show that floating direction is mainly affected by atmospheric circulations which comprise different features in different seasons in China, causing obvious floating difference:(e.g.) southwest floating dominates in summer while northwest floating in the other seasons with southwest floating dominated above 100 hPa in all of the four seasons; the maximal floating distance of over 120 km occurred in winter and the minimal one of about 40 km occurred in summer with the intermediate floating distance of near 70 km in spring and autumn. Difference in the floating distance is more significant in the eastern part of China than that in the western part. The longitudinal floating is mainly southward in winter, spring and autumn with the maximal floating distance of over 5 km occurred in spring and the averaged floating distance in winter being over 3 km and that in autumn being over 2 km. In summer the longitudinal floating is affected by the large scale circulation which causes a northward floating with the maximum distance of 1 km reached below 200 hPa and southward floating is predominated above 200 hPa instead with the farthest distance of 3 km reached. The latitudinal floating is mainly eastward with the maximal floating distance of over 77 km in winter and the minimal floating distance of near 13 km in summer as well as the intermediate distances of 49 km in spring and of 46 km in autumn. The latitudinal floating dimensions are far bigger than those of the longitudinal floating with the yearly average latitudinal floating of near 60 km and the yearly average longitudinal floating of near 3.5 km. As a result, the latitudinal floating is dominant. There exists an increasing trend of floating distances from the lower to higher levels with the floating dimensions extended westwards with the increasing height. As a whole, the floating dimensions are large and the distribution is more uniform. Also in this paper, the study for the case of typical low-level jet stream existence is addressed to analyze balloon floating with the result that the issues related balloon floating are unable to be ignored.