Seasonality is one of the significant features in tourism market. This study employs the X-13 ARIMA-SEATS method to tourism market in Taiwan. Tourists who had come to Taiwan from 1981 to 2016 mainly came from Asia, followed by the Americas and Europe. In Asian area, tourists from Mainland China account for the highest percentage, followed by Hong Kong and Japan, whose overall resources provide favourable conditions for industrial development. Rapid growth in the number of tourists coming to Taiwan gives rise to the issue of uniform distribution of tourists during the year, namely, tourism seasonality. The empirical results show that tourism seasonality of tourists coming to Taiwan is randomly changing. Analysis should be conducted concerning sustainable planning, environmental dynamic carrying capacity and sustainable development. The high tourism seasons are March, April, November and December. However, January, July and September every year are off-season in Taiwan's tourism market, with gradual decreasing number of tourists compared with those in high-season months. The contribution of this research is the analysis of data from high-season and off-season months, The local transport routes and environmental facilities can be planned for the high-season months, in order to develop diversified tourism marketing and strategies, improve the utilisation of space, and enhance business performance. During off-season months, Stay at Home Economic may be developed through Internet or platform marketing to provide distance-free remote services. For the overall environment, The analysis between off-season and high-season months not only helps to generate economic development, but can provide a sustainable planning direction, and link environmental dynamic carrying capacity and sustainable development.