The utility model relates to a low-viscosity fuel pressurization device of an internal combustion engine. The pressurization device comprises at least two work units in parallel connection, wherein each work unit includes a pressure-resistant casing; the inside space of the pressure-resistant casing is divided into two cavities not communicated with each other by an isolation element; one cavity serves as a work cavity for storing fuel; the other cavity serves as a pressurization cavity for storing liquid-state pressurization medium; the isolation element can generate free deformation or freedisplacement under the pressure difference between the pressurization cavity and the work cavity; the work cavity is connected with an oil inlet channel and an oil outlet channel in parallel; the oilinlet channel is connected with a fuel inlet through an inlet check valve; the oil outlet channel is connected with a fuel outlet through an outlet check valve; the pressurization cavity is connectedwith a medium outlet of a reversing element; the high-pressure outlet of the reversing element is connected with a high-pressure pump; and the oil return hole of the reversing element is connected with a medium box. The low-viscosity fuel pressurization device can pressurize low-viscosity fuel indirectly to obviate the leakage and abrasion of a plunger, thereby greatly improving the reliability and prolonging the service life of the system.