This work aims to study the essential oil and its main constituents of O. syriacum grown wild in 22 locations in Saint Katherine Protectorate. Origanum syriacum ssp. sinaicum plants collected during the summer season of 2014 from 22 locations in Saint Katherine Protectorate (SPK), South Sinai Egypt. Depending on location length, each location was divided into 2 stands to reach a total of 44 stands. Twenty compounds were identified as the main constituents of the essential oil which accounted for ca 97% from the total compounds of the essential oil. Carvacrol was the major constituent in all collected plants and ranged from 74.2% to 92.68% from the total compounds of the essential oil. Where, P-cymene was identified in the essential oil of all studied stands and ranged for 0.98% to 6.23%. The same was observed for γ-terpinene that was identified in the essential oil of all plants in the 44 stands and accounted for 1.37% as minimum percent up to 7.4% as maximum percent from the total compounds. The oxygenated compounds in the essential oilof O. syriacum were identified as carvacrol, terpienol-4, linalool, borneol, thymol, eugenol, and long pineneepoxid with relative percentage from 76.6%to 94.2%. The non-oxygenated compounds hydrocarbons ranged from 3.7% to18.4% in which P–cymene and ɣ-terpinene were the main non-oxygenated compounds. The relations between the essential oil%, as well as between carvacrol% in the essential oil in the different stands and calcium content, Cl and Na in the soil of the different stands were studied. In conclusion, the essential oil % of O. syriacum ssp. sinaicum and its main constituents changed according to the altitude and soil contents.