With the development of virtual reality (VR) and augmented reality (AR) technologies, the Metaverse is rapidly emerging as a platform that integrates the physical and digital worlds. The Metaverse is typically composed of multiple virtual spaces (VSs), and these VSs are independent of each other. Given the needs of users, cross-domain authentication and transactions have become a key issue. In addition, after transactions, the change of asset ownership is also an important function to be implemented. However, most existing schemes are unable to solve all of the aforementioned problems. Therefore, this paper proposes a double-layer blockchain-assisted cross-domain authentication and transaction scheme. Specifically, an intra-domain blockchain manages avatars’ registration and digital asset information while an inter-domain blockchain stores avatars’ cross-domain details. The scheme considers three possible scenarios during the process of cross-domain authentication and transaction. Furthermore, the scheme realizes the change of digital asset ownership after transactions. The security of the proposed scheme is verified using the automatic cryptographic protocol verifier ProVerif. Compared with relevant existing schemes, the proposed scheme has lower energy consumption and security risks.