Fast focusing methods and devices for multi-spectral imaging are disclosed. The method comprising selecting one of a plurality of imaging channel as a reference channel, adjusting rotation positions of a stepper motor, calculating focus measures corresponding to all rotation positions of the stepper motor, and obtaining a first distribution curve; in each of the other imaging channels, selecting at least three rotation positions of the stepper motor, matching focus measures at the selected rotation positions with the first distribution curve to obtain a second distribution curve and a offset value between the first distribution curve and the second distribution curve, and calculating a clear focusing position of the imaging channel to be focused according to the offset value; performing a fine-tuning focusing, and thereby obtaining a more precise clear focusing position. A fast focusing for multi-spectral imaging and obtain clear multi-spectral images is obtained.