A pressure reduction apparatus for solid particle-containing high pressure liquids is described. The apparatus includes a gas and liquid pressure reduction tower having a gas phase zone and a liquid phase zone, a high pressure gas and liquid separation tower which has a gas phase zone connected to the gas phase zone of said gas and liquid pressure reduction tower through a first line provided with a high pressure gas charge or discharge valve, and a liquid phase zone connected to the liquid phase zone of said gas and liquid pressure reduction tower through a second line having a feed valve for liquid being reduced, and a low pressure gas and liquid separation tower which has a gas phase zone connected to the gas phase zone through a third line having a low pressure gas charge or discharge valve, and a liquid phase zone connected to the liquid phase zone through a fourth line having a valve through which a pressure reduced liquid is discharged. Prior to opening of the feed valve or the pressure-reduced liquid discharge valve, the high pressure gas charge or discharge valve, or the low pressure gas charge or discharge valve is opened thereby increasing or decreasing the pressure within a corresponding gas and liquid separation tower.