The emergence of digital currency is seen as another major revolution in the form of currency and is expected to become the main currency and important financial infrastructure in the era of digital economy. It is imperative for central banks to promote the issuance of central bank digital currency (CBDC). Based on initial achievements of research on digital fiat currency (DFC) conducted by the People's Bank of China, this paper explores a closed loop which encompasses DFC issuance, transfer and return in the "central bank-commercial banks" binary model. Moreover, the paper designs the encrypted character string of CBDC, the issuance/return mechanism based on a 1:1 exchange ratio between deposit reserve and DFC, and the conversion mechanism of CBDC during its transfer. The paper goes on to explore the overall architecture, system architecture and technical architecture of the prototype and discusses possible ways to improve the usability of distributed ledger technology (DLT) based on partial application of DLT. Finally, this paper explores data analysis of CBDC under the prerequisite of consumer privacy protection, and concludes that consensus of distributed ledger and SM2 algorithm are key factors influencing the performance of CBDC transfer. Some suggestions for further improvement are also offered.