We propose a simple and effective even equivalent wavelength Fourier transform algorithm to improve resolution of vibration measurement in an equivalent wavelength self-mixing interferometer under a weak feedback regime. The principle of the even equivalent wavelength Fourier transform algorithm is introduced in detail. Without adding modulation or any additional optical elements, the resolution is scalable and could be enhanced to ∼0.04  nm at the 10th equivalent. The corresponding minimum measurable vibration amplitude is theoretically ∼0.13  nm. The influence factors are also discussed. The validity of the proposed algorithm is demonstrated using simulated signals and confirmed by experimental measurements at different vibration amplitudes.