This paper proposes an extending dynamic range method for infrared finger vein image acquisition by multi-light-intensity imaging. The captured images contain high dynamic range by different light intensity irradiating. The fast switch of light-intensity is synchronous with the camera imaging and the current image illumination analysis, these ensure the light intensity is automatic regulated and the captured images are in pixel-level registration. The experiment shows the proposed acquisition method is effective and the captured multi-light-intensity finger vein images are convenient for image fusion and subsequent processing.