The NFC wallet is more popular in the world than before. Many people want to have a convenient payment in shop- ping, so the NFC wallet becomes an excellent choice for them. The NFC wallet uses the Card Emulation mode to achieve the transaction process. However, the Card Emulation mode does not have the specified secure trans- action protocol. Our research provides a secure transac- tion protocol for the Card Emulation mode. It applies the Diffie-Hellman Key Exchange method and Elliptic Curve Cryptosystem to the protocol. It not only fulfills five se- cure requirements which are Data Confidentiality, Data Integrity, Unobservability, Unlinkability and Traceability, but also has the less calculation size and amount of trans- ference than another proposed method. It is more suit- able for mobile devices which do not have high calculation ability and storage space.