The measurement of fluid flow rate and temperature inside pipelines plays an important role in industrial production and engineering applications. A one-dimensional steady-state heat transfer model for high temperature pipelines is used to investigate the variation of temperature of the outer wall of a pipeline with different fluid flow rate and temperature. On the basis of the temperature of the outer wall of a pipeline, a L-M algorithm is used to study the single parameter identification of fluid flow rate and temperature in the pipeline. The influence of temperature measurement point number on the identification result is analyzed. The results show that the fluid flow rate or temperature corresponds to the temperature of the related measurement point. The smaller the fluid flow rate is, the larger the fluid temperature is, and the higher the fluid flow rate identification accuracy is. The larger the fluid flow rate is, the larger the fluid temperature is, and the higher the fluid temperature identification accuracy is. The single parameter identification results of fluid flow rate and temperature are very accurate regardless of the existence of temperature measurement errors.