The invention discloses amifostine slow-release microspheres for subcutaneous injection and a preparation method thereof. A unique two-way emulsion-solution evaporation technology is adopted, the prepared amifostine slow-release microspheres for subcutaneous injection can reach relative constant and long-acting drug release in a subcutaneous injection scene, in-vitro release is even, release time can be as long as 300 hours or above, the protection function is stable, adverse factors brought by the fact that existing amifostine can only adopt an intravenous injection drug application mode are avoided, and the problem that drug release is not uniform and lasting through subcutaneous injection is also solved.