With high-pressure jet grouting plugging technology for complex formations， a jet grouting tool with special nozzles is designed to drill through complex formations， especially multi-layer complex formations and deep complex formations where drilling mud fails to protect hole walls. The drilling tool is lowered to the complex hole section， and cement slurry is hydraulically injected by the mud pump， and sent out continuously through the tool at high pressure to cut the hole wall at the collapsed section where broken rock and soil from the unstable hole wall is mixed cement slurry. After waiting for setting， a columnar cement-rock-soil mixture with irregular diameter is formed at the collapsed hole section. After re-drilling， a “cement casing” with some strength is formed to achieve wall protection at the same diameter. The design， cement slurry formula， process principle， technical points， operation essentials and field application effects of the technology are introduced in detail.