The research aims to clarify the variation characteristics of the thermal growing season in Beijing under the background of global warming. The authors adopted correlation analysis,Mann - Kendall test and linear regression method to study the timing,length,and thermal intensity of the climatic growing season and their relationship with temperature changes based on daily meteorological data of Beijing Observatory stations during 1951 - 2016. The results showed that: the start of climatic growing season was significantly advanced and the end of climatic growing season was significantly delayed,as a result,the length of the growing season was significantly prolonged. The average temperature and accumulated temperature of climate growing season significantly increased with climate trend rate of 0.21℃ /10a and 106.5℃·d /10a respectively. However,the precipitation decreased significantly with the linear - change - rate of - 31.4mm/10a. There was a significant correlation between the indices of climate growing season and the average temperature which showed that the growing season length is consistent with the thermal conditions of the growing season. The results also showed that the trend of thermal growing season in Beijing is credible despite the heat island effect. The long - term climate change leads to an increase in agricultural thermal resources which is of great significance to improve the output and quality of agricultural products. The results have great values to the reasonable use of heat resources and planting structure adjustment.