On basis of the engineering practical experience in the crossing of the deep weathered channel of Xiang’an subsea tunnel in Xiamen, China, the author presents such assistant construction measures as advance geology forecasting, waterresistant gate installing, large pipe roof construction and fullface curtain grouting that are taken with such risks as disastrous mud burst, water burst, collapse, ground subsidence and sea water inflow. Due to the abovementioned measures, the tunnel crosses the deep weathered channel successfully.