A series of extensive laboratory experiments were conducted to investigate the transport and mixing of instantaneous discharge of unsorted particle cloud in cross-flow. The following experimental results were obtained: (1) the vertical frontal position and the longitudinal width of the particle cloud in the cross-flow is much larger than those in stagnant water, (2) the smaller cross-flow velocity will normally cause the larger non-dimensional frontal position for the same particle size range and initial volume, (3) the non-dimensional longitudinal width of the particle cloud in the cross-flow increases with the increase of cross-flow velocity. The empirical constants (α1, α3 and α2) and their variance range, which can be used to determine the relationships of non-dimensional vertical frontal position and time, longitudinal width and time, and vertical frontal position and longitudinal width were also obtained through the analysis of experimental data.