The effects of different NH4+-N to NO3--N ratio (NH4+ /NO3-) (0, 1/8, 1/4 and 1/2) on growth and quality of bunching onion (Allium fistulosum L. var. caespitosum Makino) under high temperature stress (34°C/26°C, day/night) were studied in growth chamber by hydroponics. The results showed that the growth and quality of bunching onion were affected by NH4+ /NO3-. Plant weight and height, leaf number per plant were the highest in the treatment which NH4+ /NO3- was 1/8, and those in treatment without NH4+-N were higher than in other 2 treatments. With the NH4+ /NO3- increasing, nitrate concentration in bunching onion decreased. The concentration of vitamin C was the highest in the treatment which NH4+ /NO3- was 1/8, while concentration of soluble sugar, soluble protein and allicin were the highest in the treatment which NH4+ /NO3-was 1/2. Thus the growth and quality of bunching onion were better in the NH4+ /NO3- range of 1/8 to 1/4.