The transmission fluctuation spectrometry (TFS), a new method can measure the particle size distribution (PSD) and particle concentration simultaneously in twophase fluid system. With simple optical arrangement and easy operation, the method can be applied to realtime, online measurements. The transmission signal with fluctuations are analyzed by using a second order low pass filter (LPF), and the experimental data of transmission fluctuation spectra in the frequency domain are obtained. The particle size distributions and concentrations are extracted from the experimental data with the modified Chahine iterations. Effects on the spectra of transmission fluctuations of the high concentration are discussed. The high concentration correction includes frequency response to characteristic function and step height of the transition function. Parameters for the high concentration correction are achieved and further employed in the inversion algorithm, and reasonable measurement results are obtained. Analysis to the measurement data shows that, with the high-concentration correction, the particle size distribution and particle concentration can be recovered within a broad dynamic range and the largest measurable particle volume concentration depends on the particle size.