Abstract: In this study, a solution culture experiment of potassium was carried out to investigate the effects of potassium on growth, photosynthetic characteristics and quality of garlic seedling. There were five different K+ contents, 0, 3.0, 6.0, 9.0 and 12.0 mmol/L, in the experiment. The results indicate that in the range of 06.0 mmol/L, the garlic seedling increment, pigment content, net photosynthesis rate, soluble protein and allicin contents are increased with increasing concentration of K+, and then decreased with increasing concentrations of K+ between 6.012.0 mmol/L. When potassium concentration is 6.0 mmol/L, the increment of leaves and pseudostem in garlic are the highest, the photosynthetic pigment content and photosythetic parameters (Pn, E) have similar changes, and the allicin contents in stem and leaves reach to their maxima and increased by 63.57% and 62.04% respectively compared with the treatment of 0 mmol/L K+ concentration. The soluble protein content of leaves under the 6.0mmol/L treatment is higher than those of the other treatments remarkably. The soluble sugar contents of leaves and pseudostem are the highest in the treatment of 9.0 mmol/L K+ concentration. The differences of K+ treatments on free amino acid are not significant, and the content of free amino acid are lower than that of the treatment without potassium considerably. In conclusion, potassium could promote the growth of pseudostem and leaves, chlorophyll content, photosynthetic characteristics, and improve the quality of garlic at the seedling stage. However, the effects greatly are related to the K+ concentration.