The phenomenon of the shadow economy represents a threat to the national economy in most countries because it is high rates of gross national product., Which includes all economic activities practiced by individuals or companies have been not recorded officially and not intervened in the national income accounts also it not subject to the administrative and legal systems , it will leads to mislead in statistics and information and making it inaccurate and shows not true potential of the state, which in turn lead to the misallocation of economic resources and the gross national product. This research aims to study the causes of this phenomenon and ways of tackling them in Syria.