Changing diffusers are most commonly used for laser speckle reduction. Here, a weak-scattering static diffuser (WSSD) is proposed and demonstrated by fast pumping poly(methyl methacrylate) nanoparticles in a long distance using microfluidic flow. Experimental results show that this proof-of-concept device can effectively reduce speckle, where the lowest speckle contrast ratio is 0.04. Comparing with vibrating/rotating diffusers driven by mechanical motors for speckle reduction, the WSSD is static. Moreover, the WSSD can suppress speckle with weaker light scatterings (scattering angle equals to 5.8° at the lowest speckle contrast ratio value), making it superior to vibrating/rotating diffusers driven by micro actuators. Because of these promising advantages, the WSSD has prospects of wide range of applications, such as in laser projection displays.