Such key technologies as excavation technology, controlled blasting technology, watersealing grouting technology and mud inflow treatment technology adopted in the construction of the waterrich fullyhighly weathered sandstone section of Xingwangmao tunnel are expatiated in the paper. "Top heading + 2 benches" 6step method adopted ensures the tunneling safety, controlled blasting technology adopted ensures proper protection of the surrounding ground; the watersealing grouting technology adopted ensures cuttingoff the seepage path and the mud inflow treatment technology adopted ensures proper tunnelling advance.