Bitcoin's Layer2 technology is a payment channel network based on Bitcoin, which can achieve fast, low-cost small payments while providing better privacy protection. Bitcoin's usage scenarios and value have been enhanced through the development of Layer2 solutions and decentralized financial ecology. Currently, hundreds of decentralized applications are built on the Bitcoin second-layer network, including Lightning Network, Liquid Network, RSK and Stacks, etc. Investors need to consider technical risks fully, user acceptance and education costs, and adopt risk management and strategic planning to ensure sustainability and long-term returns of their investments.