The increase of high-speed railway operation speed will intensify the pantograph-catenary（PC） vibration

and increase the frequent offline and arc. The burning intensity and extinguishment characteristics of arc plasma are influenced by temperature.Consequently

based on the spectral diagnosis

the temperature variation of PC arc plasma due to the lowering pantograph was studied. Meanwhile

the temperature rise of pantograph slide and catenary wire was also studied by the infrared thermal image. The voltage and current waveforms during pantograph-lowering process were recorded by a pantograph-catenary arc test apparatus. The emission spectrum of the PC arc plasma was collected and based on the Boltzmann plot

and the variation of excitation temperature during pantograph-lowering process was calculated and analyzed. Moreover

the impact of current on excitation temperature was also studied

and the temperature of pantograph slide and catenary wire were acquired. The results show that

at the current range of 16～22 A

the initial arc voltage is distributed between 30 and 36 V. The voltage increases linearly with the increase of pantograph catenary gap. The temperature of pantograph-catenary arc plasma decreases gradually during the pantograph-lowering process at the same current. However

the temperature increases with the increasing of current at the same gap. By IR images of pantograph slide and catenary wire

the temperature of catenary wire is consistently higher than that of pantograph slide and the increase trend of highest temperature gradually moderates during the whole pantograph-lowering process.