Abstract: The climatic growing season is the stable period through the thresholds of daily mean temperatures，viewed as the entire stage in which growth can be theoretically take place. Assessing its spatio-temporal characteristics of different vegetation zones specifically may have an useful meaning and have several important climatological applications. The paper investigated the temporal and spatial changes of the growing seasons in different vegetation zones using mean air temperature data recorded at 46 stations in Inner Mongolia，China，over the period 1961-2010. Mann-Kendall trend test and linear regression method are also used to detect the significance and the magnitude of the growing season change，respectively. Results show that the length of the growing season in desert zone had the maximum extension and inter-annual fluctuation over the past 50 years，with the amount of 22 days and 13 days respectively. In grassland zone，the length has increased by approximately 14 days，mainly owing to an earlier onset in spring（accounting for 75%），and the magnitude of increase became larger from east to west，with an rising inter-annual fluctuation. While the length in agriculture and forest regions were about 17 days and 15 days，respectively，with almost identical rates of an earlier onset in spring and a delayed end in autumn. The results also suggest that a continuous advancing trend of the growing season may provide opportunities for planting earlier，ensure crop maturation，and promote planting range of high-yield and fine quality crops extending，but the options should be taken timely and scienti?cally to cope with ongoing climate change，based on the characteristics of the growing season fluctuations over the 50 years.

Key words: climate change, vegetation zones, growing season change, Inner Mongolia