The experiments of this study were conducted to investigate the effect of magnetized water and two other chemical substances thatare kown as Agro promotor1 (substance No.48) and Agro promotor2 (substance No.50) on growth, yield and chemical composition of onion variety Giza 6. The sesubstances were obtained from Cairo University. Result revealed that growth parameters, yield and its component and chemical contents increased with using both of magnetic water and Agro promotor1 (substance No.48) at concentration of 3 ml/l comparing with control (untreated) treatment. Using magnetized water and Agro promotor1 (substance No.48) at concentration of 3 ml/l induced positive significant effect on plant height and weight, number of leaves/plant and bulb diameter as well as significantly improved neck and bulb diameters, bulb weight, total soluble soiled, total yield and marketable yield percentage than plants of control treatment which showed an increase in percentage of bolters, in both season. In general, it might be concluded that application of each of magnetized water and Agro promotor1 (substance No.48) treatments proved to be good technology to enhance growth, yield and quality when compare with untreated treatment. The marketable yield was increased by 30% as compared with control treatment by using magnetized water and increased by 22-235% when substance No.48 at concentration of 3 ml/l was used. The increase in total yield ranged from 12-15.4% when using magnetized water and was 14-15.4% when substance No.48 at concentration of 3 ml/l compared with control treatment. This study recommends using magnetized water to obtain the highest marketable yield and the lowest percentage of bolters. In case of magnetized water un-available, Agro promotor1 (substance No.48) at concentration of 3 ml/l can be applied