Transmission fluctuation spectrometry with temporal or sptail correlation is being developed as a new method of particle size analysis, in which the particle size distribution and particle concentration can be measured simultaneously, and real-time online measurements can be realized. As the particle concentration increases, the measured transmission fluctuation spectrum deviates gradually from the theory due to the effects of high particle concentration. The high-concentration effects of transmission fluctuation spectrometry with temporal correlation (TFS-TC) are studied with numerical simulation whereby an infinitesimally thin beam is employed and some experimental evidence is also presented. As a result, the correlation spectrum is affected only by the monolayer structure. As the particle concentration increases, the transition function deviates from the theory and shifts to the range of smaller dimensionless correlation time gradually, the step height of the trasition function is unchanged.