The orifice plate has the advantages of convenient construction, high energy dissipation efficiency, and economy, and is widely used in hydropower engineering and discharge engineering. The recovery length of the flow pressure behind the orifice plate is related to the distance arrangement between orifice plates in multi-stage orifice plate design. However, little research has been conducted on the pressure recovery length behind the orifice plate. The numerical simulation method is used to quantitatively study the influencing factors of the pressure recovery length behind the orifice plate, and the results show that the recovery length of the flow pressure behind the orifice plate is mainly dominated by the aperture ratio of orifice plate, the relative thickness of the orifice plate, and the Reynolds number of fluids flowing through orifice plate. As the Reynolds number increases to a fixed value, the pressure recovery length behind the orifice plate does not change. When the relative thickness of the aperture ratio of the orifice plate are within a certain range, the relative thickness of the orifice plate will not change, the aperture ratio of the orifice plate decreases, and the pressure recovery length behind the orifice plate increases. As the diameter ratio of orifice plate remains unchanged, the relative thickness of the orifice plate increases, and the pressure recovery length behind the orifice plate decreases. The empirical formula for the pressure recovery length behind the orifice plate is obtained by multivariate regression analysis and curve fitting, and the indoor test verification is adopted, which provide theoretical basis for distance arrangement between orifice plates in multi-stage orifice plate design.