By reviewing the deep foundation excavation case for a gate shaft connecting with the water intake tunnel of a nuclear power plant, this paper describes the scheme choosing of foundation excavation supports in rocksoil combinational condition, and also introduces key points of design and calculation for double-row piles supports, key points for dewatering and drainage of foundation excavation, monitoring item, and final actual performance of the foundation excavation. The result shows that the foundation excavation in topsoil and subrock can be supported in two layers, a platform should be arranged between the topsoil and subrock, double-row piles with no strut combined with cutoff is suitable for the rock-soil combinational ground with topsoil of sand and coral reef fragment, underlayer of moderate or highly weathered rock .