This research was conducted at the National Research Center greenhouse ring two consecutive seasons of 2013/2014 and 2014/2015, in order to study the effect of irrigation water types (tap water, magnetized water) and levels of ammonium sulfate (0, 7, and 14 g / pot) and their interaction, on the vegetative growth and oil production of marjoram (Majorana hortensis L.) plant. The results showed that marjoram plants responded significantly to the different types of irrigation, as well as nitrogen fertilization and their interaction. Irrigation by magnetized water showed that a significant increase in vegetative growth; i.e. plant height, number of branches, fresh and dry weights of herb, stem, leaves and roots per plant and root length. Using nitrogen fertilizer rates gave significant increases in vegetative growth parameters, where the best treatment one was 14 g/pot. As for the interaction between types of irrigation water and nitrogen fertilizer rates, data showed that plants irrigated with magnetized water with addition of ammonium sulfate at a rate of 14 g/pot recorded the highest values ​​of the attributes of vegetative growth, production of oil, major compounds of oil and chemical components of marjoram plant. Magnetic water treatment with the addition of 14 g / pot ammonium sulfate recorded 43.38% of the terpineol-4-ol (the main compound of the oil), while irrigation with tap water recorded 26.41%. Also this treatment increased some compounds of marjoram oil percent; such as α-myrcene, α-terpinene, α-phellandrene, Ç-terpinene, α –terpinolene, L-linalool, α-terpineol and linalyl acetate with mean values of 1.08, 5.91, 1.13, 12.45, 2.40, 3.48, 3.53 and 6.35 compared to tap water treatment, which gave 0.89, 4.31, 1.08, 8.81, 1.91, 2.64, 2.97 and 5.66 for these components; respectively. The obtained results also indicated the possibility of obtaining the highest values ​​of chemical constituents such as total carbohydrates, nitrogen, phosphorus and potassium percentages when plants were irrigated with magnetized water with the addition of ammonium sulfate at a rate of 14 g / plant under the conditions of the experiment.