Abstract：With the advent of bitcoin，digital currency began to enter the public vision.As a decentralized payment infrastructure that supports the innovation of digital finance，digital currency trades through data，and plays the functions of circulation means，accounting unit and value storage.In recent years，the mode of global monetary payment and settlement has been constantly changing，and the payment method is rapidly evolving from tangible cash transaction to electronic non-cash transaction.The change of monetary form is increasingly obvious.

Based on the integrated application of blockchain，AI，cloud computing，large number and other new generation information technologies，digital currency will be a rich industrial ecology from，which will promote the development of digital economy such as digital finance and e-commerce，and lead to the formation of new formats and business models.In this context，the private digital currency has been continuously innovated and developed.Facebook's new crypto currency Libra is a typical example.Due to the credit guarantee equivalent to the endorsement of the central bank，its super sovereign currency features are further demonstrated.Although at present，the private digital currency is still restricted by multiple financial regulatory authorities，its innovation pace will not stop.

The issue of digital legal currency by sovereign countries conforms to the development trend of digital finance and digital economy.However，considering the stability and risk of financial infrastructure，the report analyzes and enumerates in detail the impact and advantages and disadvantages of the introduction of digital legal currency in technology，commerce and economy，finance，cross-border payment and international trade.At present，although most of the world's central banks have started to issue digital legal currency，the central banks of major economies have not decided when to officially introduce digital legal currency.In the face of the development and innovation of digital currency in the future，China should speed up the improvement of private digital currency supervision，strengthen the research and pilot of digital RMB，but should not rush to issue，but give priority to the cooperation with relevant countries，regional international alliances and international organizations to issue regional cross-border digital currency.

Key words：Digital Currency；Innovation；Blockchain；Private Digital Currency；Digital Fiat Currency