After introducing the real-time temperature measurement system using lasers In-GaAs/I and pyroelectric detector LiTaO3, this paper mainly discusses the effect and control on temperature measurement accuracy by the radiation of the detector system itself. Three measures on improving temperature measurement accuracy, cooling the detector system by water, using a narrow band filter with the bandwidth of 150 nm and making electrical compensation, are presented. Some necessary calculations and analysis are given. Experimental results also show that temperature measurement accuracy is suitable for our requirement in the range of 400℃-1200℃ after taking these measures above.