As the main index of ground sensible heat flux, the ground-air temperature difference(GATD) is the most important component in the surface heat balance. Observation data of ground temperature, surface air temperature,wind speed,precipitation, sunshine hours,evaporation and relative humidity,which were obtained from 9 meteorological stations in Shanghai during 19612015,were used to analysis the changing characteristics of GATD and its impact factors. The results show that: (1) GATD in Shanghai is biggest in summer and minimum in winter,and shows the characteristics of increasing from the center of the city to the suburbs in all seasons. (2) Due to the air temperatures faster rising rate than ground temperature, the annual average GATD is slowly decreased in Shanghai,with the most obvious decreasing season in summer and the most significantly region in urban and suburban areas. The absolute value of the urban heat island intensity of Shanghai showed an increasing trend,but its relative contribution to the variation of GATD showed a decreasing trend. (3) In summer and autumn the significant environmental factors affecting GATD are sunshine hours and precipitation, in spring is precipitation and in winter is average wind speed. The conclusions obtained in this paper are important to the understanding of changing characteristics of urban thermal environment under the background of climate change, and also provide a scientific reference to the protection and improvement of urban ecological environment.