Abstract: Based on the daily ground surface and air mean temperatures of five meteorological stations in Qiangtang Nature Reserve, the spatial and temporal changes of the ground surface freezing indices (GFI), ground surface thawing indices (GTI), air freezing indices (AFI) and air thawing indices (ATI) in the nature reserve in recent 49 years under the background of climate warming were analyzed by using the trend analysis and Mann-Kendall test analysis. Moreover, changes of the FTI in the next 80 years (2021~2100) are also projected under the emission scenarios of RCP4.5 and RCP8.5. The results shows that: (1) The ATI and GTI generally showed a decreasing distribution from west to east with the increase of altitude; the distribution pattern of AFI and GFI was not obvious, but the maximum value appeared in Amdo, and the minimum value occurred at different stations. (2) In the past 49 years, AFI and GFI decreased significantly at the rates of 8.97 and 10.45℃·d·a⁻¹, respectively, while ATI and GTI increased with the rate of 7.05 and 11.38℃·d·a⁻¹. The change rate of the ground surface freezing and thawing indices was greater than that of atmospheric freezing-thawing index. In contrast to the Tibetan Plateau, the AFI and GFI of Nature Reserve decreased slightly, the ATI increased nearly, and the GTI increased greatly. (3) As for the decadal characteristics of AFI and GFI experienced positive anomalies in the 1970s~1990s, as compared with negative anomalies during the 2000s-2100s, showed a decreasing characteristic, while the ATI and GTI, on the contrary, presented an increasing characteristic. (4) AFI, ATI, GFI, and GTI mutated in 2001, 1993, 1999 and 1998, respectively. The mutation time of AFI was the earliest, which was 8 years earlier than that of AFI. (5) The decrease (increase) of FI (TI) in CTNRT was closely related to the significant increase of mean temperature and mean minimum temperature, increase of precipitation, decrease of mean wind speed, as well as the decrease of snow cover days and maximum snow cover depth. (6) Under the RCP4.5 emission scenario in the next 80 years, the AFI and GFI of CTNRT will decrease by 322.8·d and 357.6℃·d, respectively, and the ATI and GTI will increase at 262.2·d and 419.7℃·d, respectively. In addition, the variability of FTI becomes greater under the RCP8.5 emission scenario.