The invention discloses a preparation technology of bean curd skin micro-fibrillated cellulose. The technology comprises the following steps: firstly, carrying out superfine grinding on bean curd skin, adding water, and hydrolyzing with protein enzyme with the mass fraction of 0.05%-2%; treating with thermokalite; further adding cellulase with the mass fraction of 0.01%-0.1% under the microwave/high-speed stirring synergistic action and treating for 60-120 minutes, so as to obtain bean curd skin micro-fibrillated slurry; homogenizing by virtue of a high-pressure homogenizer for 5-15 times to obtain micro-fibrillated cellulose; and finally, adding a surfactant with the mass fraction of 0.1%-0.5% to obtain the micro-fibrillated cellulose of which the performance is stable and the diameter is 20-80nm. The micro-fibrillated cellulose can be prepared from bean curd skin through the technology disclosed by the invention; the preparation technology is simple, economical, and free of pollution; the energy consumption can be reduced; the diameter of the micro-fibrillated cellulose is 20-80nm; the performance of the micro-fibrillated cellulose is stable; and the quality requirements of the micro-fibrillated cellulose are met.