Speckle suppression is a technical bottleneck hampering the development of laser display technology. The effects of the scattering angle of the diffuser, the number of cascade diffusers and the separations between them on the width of the scattering beam coherence area are analyzed by the experiments. On the base of the scatterer composed of cascade diffusers and lightpipe, the laser decoherence phenomena achieved by applying cascade diffusers is explained according to the multiple scattering theory. Based on statistics of integrated speckle, the relationship between the autocovariance function of the intensity and the speckle contrast is derived from the speckle pattern within the integration time T of CCD, and the influence of cascade diffusers on the displacement of the moving diffuser is determined, which contributes speckle suppression. The experimental results show that the combination of the scatterer with the moving diffuser not only improves optical energy utilization, but also reduces the speckle contrast from 0.753 to 0.069 within the integration time 1/30 s of the detector.