Sperm viability stain (eosin-aniline black method) can routinely test the viability of all sperm specimens, and identify sperm with intact cell membranes by dye rejection staining method, so as to derive the percentage of viable sperm, which consists of eosin staining solution, aniline black staining solution, and utilizes the principle of dye rejection staining, that is, the correlation is based on the damage to cell membranes such as the membrane on non-living (dead) cells, which permits a non-transmissive dye to be able to into the membrane for staining; whereas the cell membrane of living cells is able to resist the entry of dyes, resulting in dye rejection and no coloration.