Precise knowledge on temperature and its fluctuation in combustion systems are among the important energy issues in almost all industrial sectors, energy conversion and power fields. In this study, a spectroscopic technique is used to measure the time-resolved temperature distribution by a comparatively simple optical system that involved two band-pass filters (BPF), and a charge-coupled device with image intensifier (ICCD) video camera. The system was assembled and applied to an acetylene-oxygen premixed flame that are widely used for welding purposes because of very high temperature in such flames. The temperature distribution and its fluctuation directly impact the quality of soldering. The results provided direct visualization of temperature and its fluctuation in the flames that are conjectured to emanate from thermal and hydrodynamic phenomena from chemical reactions in the flame and interaction with surrounding air.