Abstract: In multiple processes of natural uranium conversion, gas-solid fluidized bed reactors are involved, and the particles therein are all high-density particles. At present, there is a lack of systematic mechanistic research on the fluidization behavior of such high-density particles, which thus requires focused investigation. A fluidization model based on the Lagrangian method, namely the DDPM (dense discrete phase model), was constructed, and the robustness of the model was verified by comparing with experimental data from cold-model fluidization tests using real materials. Flow snapshots of gas and solid phases at different time were obtained, and the pressure fluctuations in the bed were studied using statistical analysis, spectral analysis, and orthogonal experimental design methods. The results show that bubbling occurs in the bed, and vortices of the gas phase appear at the bubble positions. After the fluidization behavior is fully developed, the particle concentration is low near the distributor, while particles mostly aggregate in the middle and upper regions of the bed. The flow channels between particles are smaller in these regions, making bubbles more likely to form. During the fluidization process, slugging and channeling are obvious, which affect the sufficient contact between gas and solid phases. The expansion rate is low, and fluidization dead zones occasionally appear, indicating that the fluidization state of UO₂ particles is poor. A bubbling fluidized bed is formed in the bed, and the deviation degree is much greater than 0, suggesting uneven fluidization behavior. No obvious single peak is found, which indicates the absence of periodic bubble generation. Instead, multiple small peaks exist in the range of 0.2-10 Hz, and the main frequency of the bed corresponds to this frequency interval. In addition, based on Kolmogorov’s −5/3 law, the gas-phase flow did not reach turbulence. The continuous wavelet transform (CWT) shows a continuous coherent structure band below 20 Hz, indicating that the main frequency of the bed is concentrated in this frequency range and forms a peak band, which is consistent with the results of the multiscale analysis (MSA). After the bed fully developed, a coherent structure band along the frequency direction appears, suggesting the generation of larger bubbles. An L16 (2¹⁵) orthogonal interaction table was established. Through analysis of variance (ANOVA), it is found that full cone angle (α) and the coupling parameter (R_fb×d_p) has a significant impact on fluidization quality, while superficial gas velocity (U) has a certain impact. Other parameters and coupling parameters have little effect on fluidization quality.