Based on the Kirchhoff law, a practical temperature real-time measurement system using laser diode and LiTaO 3 pyroelectric detector was developed. According to the infrared radiation characteristics of the measurement surface, surroundings, transmission features of atmosphere and the temperature measurement system itself, detailed analyses were given on the factors of influencing temperature measurement accuracy. And the measures on improving the temperature measurement accuracy were put forward. Experimental results show that the temperature measurement inaccuracy is within 0.3%, and it is suitable for the requirements.