The invention provides compound nicotinic acid sustained-release capsules and a preparation method thereof. The compound preparation comprises 250 mg of nicotinic acid and 10 mg of simvastatin, and is prepared through the following steps: preparing blank pellets; preparing nicotinic acid sustained-release pills; preparing simvastatin immediate-release pellets; and preparing capsules. The product of the invention is suitable for treating primary hypercholesterolemia and mixed dyslipidemia; according to the respective characteristics, the nicotinic acid is used as the sustained-release ingredient and the simvastatin is used as the immediate-release ingredient, so that all the ingredients play a synergistic effect in vivo, the pharmaceutical effect is achieved furthest, the toxic and side effects of the medicine can also be reduced, and the therapeutic effect for relieving the hypercholesterolemia is obviously superior to that of any single preparation.