The transient solid particle velocity analysis in a fluidized bed combustor (FBC) freeboard is critical for its efficient and reliable operation. An experimental cold model (152 mm ID x 610 mm height) of an FBC was designed and fabricated. Transient solid particle velocities in the FBC freeboard model were measured and analyzed with the assistance of an advanced laser-based particle image velocimetry (PIV) instrumentation. The PIV was applied to the FBC cold model to visualize the transient solid particle movement in the area of interest (AOI). Sixteen particle velocity profiles were generated in a 1.6 s time period. In each profile, a 3 (columns) x 1 (row) grid was set. The regression analysis with the independent variables of X (x coordinate) and t (time) were applied to develop a specific empirical model for a transient solid particle vertical velocity component (V-y) within the AOL The model shows that the V-y within the AOI could be expressed as V-y=f{sin C1X, cos C(2)t, e(-C3t) }, where C-1, C-2, and C-3 are constants. This unique regression analysis method was proven to be very effective and practical for evaluating the experimental conditions and analyzing experimental results in FBC systems.