Abstract: The paper studied the effects of potassium fertilizer on the seed formation and quality of Zea mays Sinensis. The material was “xiangbainuo”, a kind of Zea mays Sinensis, sowed in autumn and the experience was designed to do plot test. The results showed: (1) The fresh weight, the dry weight and the volume of seed were all raised than control for 0.158 g/100seed/d, 0.136 g/100seed/d and 0.130 cm3/100seed/d, respectively, while the seed water content was more quickly declined by 0.22%; (2) Potassium fertilizer can help gaining higher the content of lysine, crude protein, free amino acid , soluble protein, Fat and Starch . ⑶14d after being pollinated, lysine and crude protein reached the max volume, then began to decline slowly; the free amino acid and the soluble protein also reached the highest, 14d after being pollinated, but then declined quickly, until the 22 day; Fat and Starch were steadily raised until the 22 day after being pollinated, then slow down. (3) The optimum harvest date of Zea mays Sinensis was the 22-26 day after being pollinated, which sowedin autumn.