The effects of chronic low-dose exposure to microcystins were preliminarily studied on sperm quality and testicular function in male mice. Microcystin-LR (MC-LR) was orally administered to male mice at 0, 1, 3.2, and 10 μg/L for 3 and 6 months. Our preliminary study found in three-month group, sperm quality declined at 3.2 and 10 μg/L doses, testosterone dropped at 10 μg/L, levels of LH and FSH increased, and Leydig cells exhibited apoptosis. Similar, but more pronounced, effects were observed in groups treated with MC-LR for 6 months. Compared to control (0 μg/L), the rate of sperm abnormality was higher and testosterone levels were lower following administration of 3.2 and 10 μg/L MC-LR and structural damage to the testis was observed with 10 μg/L dose. Thus, chronic low-dose treatment with MC-LR results in substantial toxicity to male reproduction, causing declines in sperm quality, decreased levels of serum testosterone, and injury to the testis.