Composition should be initially determined when analyzing temperature distribution using the refractive index measurement method. A method which divides the measured flow field by combining the phase and emission intensity distributions is proposed to confirm the composition of each region and significantly improve the temperature reconstruction accuracy. Candle-air (non-premixed flame) and propane-air (premixed flame) combustion flow fields are selected for the experiments. The refractive index, phase, and emission intensity distributions are matched. The composition distributions of both flow fields are analyzed and confirmed. A comparison of the temperature results obtained using the phase partition method (Model 1), emission intensity partition method (Model 2), and integrating phase and emission intensity partition method (Model 3) shows that Model 3 is the most reliable. Furthermore, the reliability and adaptability of the method are analyzed and discussed. This study provides a reference for the temperature diagnosis of complex flow fields based on refractive index measurements.