In order to effectively suppress speckles in laser projection display, a numerical expression of the optical fiber length and the optical field contrast degree at the end of the optical fiber was established based on speckle statistical theory. Based on the integral scattering statistics method, the effect of scattering and moving properties of the multiple scatter diffuser on speckle contrast was analyzed. The experimental results show that the laser speckle contrast ratio can reduce 3.76% by using the composite speckle suppression technology combining a vibrating 10 m multimode fiber with a rotating cascade diffuser. Using composite speckle suppression technique can increase the system’s freedom, which contributes to speckle suppression. This study can provide a reference for the research work of composite speckle suppression technique in laser projection display.