Effects of silt mean diameters and silt concentrations on cavitation flow are researched in a two-dimensional nozzle. Silt mean diameters are 0.02， 0.04， 0.06， 0.07 and 0.08 mm and silt concentrations are 0.02， 0.04， 0.06， 0.07 and 0.08. When silt mean diameters are invariant， silt concentrations are changed to consider the effects on cavitation flow and when silt concentrations are the constants， silt mean diameters are varied to consider the effects on cavitation flow. Results show that cavitation occurs at the beginning parts of the jet orifice and distributions of static pressure， vapor volume fraction， and silt particles are axial symmetrical. Cavitation number variations with silt concentrations or with silt mean diameters reflect the effect degree of silt particles towards cavitation flow. With silt mean diameters being 0.06， 0.07 and 0.08 mm， fluctuations of cavitation number with the increase in silt concentrations are much larger than it with silt mean diameters being 0.02 and 0.04 mm. During silt concentrations are fixed， all fluctuations of cavitation number with the increase in silt mean diameters are vaster， demonstrating that silt mean diameters have a more intense effect on cavitation flow. Reasons why silt particles promote the inception and development of cavitation are analyzed. Effects of properties of silt particles， cavitation nuclei， virtual mass force， slip velocity， Saffman lift force and turbulent kinetic energy are considered and studied.