The slope at the exit of Caijiacun tunnel of Central Yunnan Water Diversion Project is highly difficult to be supported with an excavation height about 38 m, excavation slope ratio of 1∶0.3, and a thickness of collapse deposit reaching 8 m. Having analyzed the merits and shortcomings of inter-hole delay and inter-row delay, we researched the millisecond blasting network with low single sound and low unit consumption in excavating the thick deposit of steep slope. We proposed a loosening blasting technology integrating inter-hole and inter-row delay blasting. The technology integrates the control of explosive charge in hole, the upgrading of charge structure, the optimization of initiation network and external protection. Methods of lengthening and sectional plugging, correcting the charge density of pre-splitting hole line, and reserving rock ridges are put forward. The proposed technology is demonstrated to be of sound loosening blasting effect for the thick deposit of steep slope of Central Yunnan Water Diversion Project with the blasting vibration, flying rock and dust been effectively controlled.