The development of energy sector is closely linked with the European integration. The Energy Union has been established eventually for the purpose of promoting European integration，which sets up a new energy governance framework for Europe as a whole. Under this framework，the European Union tries to shape its energy policy，external policy and climate change policy at the European level，focusing on supply security，renewable energy，energy efficiency，internal market and R&D as its priorities. The Energy Union has been listed as one of the prioritized policy areas along with Junker Investment Plan and Digital Market by the European Commission. At present，in order to keep the Energy Union running healthily，massive plans and actions towards infrastructure，energy efficiency，R&Ds as well as internal pipeline and electrical networks have been enacted. Nevertheless，due to the adoption of the EU’s State Aid Guidelines，a number of member states have changed their renewable electricity policy from a subsidiary model into a “bid-for-contract” market model，which may lead to an uncertain prospect of the renewable sector. The future development of the Energy Union will be constrained by the factors of institution and funding and the uncertainties connected with the situation in Russia.