Fluid temperature is important for the analysis of the heat transfers in thermal hydraulics. An accurate measurement or estimation of the fluid temperature in multiphase flows is challenging. This is due to that the thermocouple signal that mixes with temperature signals for each phase and non-negligible noises. This study provides a new approach to estimate the local fluid temperature in multiphase flows using experimental time-series temperature signal. The thermocouple signal is considered to be a sequence with Markov property and the particle filter method is utilized in the new method to extract the fluid temperature. A complete description of the new method is presented in this article.