A fingerprint image processing method, applied in an optical fingerprint identification system of an electronic device, wherein the electronic device comprises a display panel, the display panel comprises a display pixel array, the optical fingerprint identification system comprises an image sensing array, the image sensing array is disposed under the display pixel array, characterized in that , the fingerprint image processing method comprises: obtaining a first background image and obtaining at least an interfering frequency (f I,1 -f I,N ) when the display panel is not pressed by a finger of a user , wherein the step of obtaining the at least an interfering frequency comprises: obtaining a second background image, wherein no fingerprint image is included in the first background image and the second background image ; performing a subtracting operation and a transforming operation on the first background image and the second background image, to obtain a difference image spectrum (Diff_IM_SPM), wherein the transformation operation is a Fast Fourier Transform; and performing an energy detection operation on the difference image spectrum, to derive the at least an interfering frequency from energy spectrum of the difference image spectrum; receiving a received image when the display panel is pressed by the finger of the user ; performing a subtracting operation on the received image and the first background image, to obtain a difference image ; and performing a filtering operation on the difference image at the at least an interfering frequency to filter out the interference, to obtain an operational result ; wherein the optical fingerprint identification system determines a fingerprint within the received image according to the operational result. obtaining a first background image and obtaining at least an interfering frequency (f I,1 -f I,N ) when the display panel is not pressed by a finger of a user , wherein the step of obtaining the at least an interfering frequency comprises: obtaining a second background image, wherein no fingerprint image is included in the first background image and the second background image ; performing a subtracting operation and a transforming operation on the first background image and the second background image, to obtain a difference image spectrum (Diff_IM_SPM), wherein the transformation operation is a Fast Fourier Transform; and performing an energy detection operation on the difference image spectrum, to derive the at least an interfering frequency from energy spectrum of the difference image spectrum; obtaining a second background image, wherein no fingerprint image is included in the first background image and the second background image ; performing a subtracting operation and a transforming operation on the first background image and the second background image, to obtain a difference image spectrum (Diff_IM_SPM), wherein the transformation operation is a Fast Fourier Transform; and performing an energy detection operation on the difference image spectrum, to derive the at least an interfering frequency from energy spectrum of the difference image spectrum; receiving a received image when the display panel is pressed by the finger of the user ; performing a subtracting operation on the received image and the first background image, to obtain a difference image ; and performing a filtering operation on the difference image at the at least an interfering frequency to filter out the interference, to obtain an operational result ; wherein the optical fingerprint identification system determines a fingerprint within the received image according to the operational result. <EOS>