The security of energy supply is one of the most important factors in the development of the European Union’s (EU) energy policies. The security of energy supply has become the most important agenda in the energy field of EU because EU countries in natural gas import significantly depend on Russia and the energy crises between Russia and Ukraine affect EU countries negatively and the flow of energy that reaches from Russia to EU countries is often interrupted. The EU has focused more on the policies that will ensure the security of energy supply and reduce its dependence on the supplier countries in 2000's. From the combat of global warming and environmental pollution to increase of energy saving the regulations in many field supporting the security of energy supply have been implemented. This study elaborates generally the impact of energy crises on the development of the EU’s energy policy and mentions its efforts to create energy policy from the establishment of the EU.