The invention discloses a microemulsion for prevention constipation of diabetics and a preparation method thereof, and relates to the field of healthcare food. The microemulsion comprises: 20-30% of camellia oil, 30-40% of surfactant, 0.1-3.0% of fructo-oligose, 0.1-1.0% of stachyose, 0.01-0.05% of preservative, and 0.5-1.0% of acidulant, with the balance being glycerin and distilled water. The preparation method comprises steps of dissolving the fructo-oligose, the stachyose, the preservative and the acidulant into the distilled water, then uniformly mixing them with the glycerin, adding Tween-80 to obtain a clear transparent solution; mixing the camellia oil with Span-80 to obtain a yellow clear solution; adding the clear transparent solution into the yellow clear solution to obtain a clear orange-yellow microemulsion. Comparing to prior arts, the microemulsion for preventing constipation of diabetics does not contain sugar, so it is not only of a good effect, but also is free of toxin and side effects. With a good taste and an attractive appearance, the microemulsion for preventing constipation of diabetics is an ideal functional food for diabetics to coordinate intestines and stomach as well as prevent constipation.