By using the gravity center model, Gini coefficient and correlation analysis, this paper discusses the time and spatial law of the seasonality of the whole inbound tourist market and segmentations in the main tourism cities in the mainland China. The research finds that the gravity center of the foreigner market moves to a further north position, that of Hong KongMacauTaiwan market moves to a further south position, the former market leads the change pattern of the gravity center of the whole inbound market, however, each city has its inbound tourists advantage, which make the whole market gravity close to geographic gravity. The seasonality intensity varies from one market, region and destination type to another, each city holds its advantage in some market depending on its greater tourist volume. The timeseries pattern of seasonality is quite different from each market, institutional factors play more important role than natural factors in the disparity. The spatial law of the seasonality of different markets is different and results from the different spatialtime behaviors of the tourists. Finally, some suggestions, such as enriching tourism products, subdividing market and inter regional joint marketing, are made to deal with the seasonality problem.