The invention discloses a noise pre-estimating system for pre-estimating noise of a single-phase oil-immersed transformer. The system includes a transformer component finite element unit for determining a solid unit stiffness matrix KS, a damping matrix CS and a mass matrix MS relevant to a solid; a fluid acoustic finite element unit which establishes a fluid acoustic finite element equation according to air parameters out of a box and a transformer internal fluid field; a solid and fluid coupling unit which establishes a solid and fluid coupling dynamic equation; a test unit which includes an optical fiber accelerometer, an acquisition instrument and a sound meter; an electromagnetic excitation analog input unit to which excitation vectors of a plurality of harmonic components of a solid structure are applied; and a data correction unit which takes the solid and fluid coupling dynamic equation as a pre-estimating model, and uses an acoustic model and a difference to calculate the coupling dynamic equation so as to obtain a sound pressure of a sensitive point.