The article discusses Bitcoin Layer2 solutions, which are mainly divided into two categories: sidechain and UTXO+ client verification. Sidechains such as Stacks, RSK, Liquid Network and Lightning Network aim to increase transaction speed and scalability, but face centralization and security challenges. UTXO+ client verification attempts to achieve Layer2 ledger sharing while maintaining the characteristics of Bitcoin, but its technical implementation is difficult. The RGB and RGB++ projects attempt to ensure asset security through client-side verification, while BitVM proposes theoretical concepts to enhance Bitcoin's programmability. The article points out that despite the promising prospects of Bitcoin Layer2, most projects are still in their early stages.