In relation to the gate shaft excavation at a water conservancy project where the excavation size is 2 m×2 m for the shaft pilot hole， this paper introduces a new excavation method-the one shot blasting method for sinking of the central pilot hole with emphasis on the technical measures on how to complete the central pilot hole by one-time blasting. With this method， one shot blasting for the central pilot hole is combined with expanding excavation around the hole. The deep hole blasting method is adopted for excavation. Through the design of the blasting scheme， preparation before construction， mechanical drilling， charging， wire connection， blasting， safety inspection after blasting and other processes， the central pilot hole is first excavated and shaped by one shot blasting， and then it is expanded and shaped by shallow hole multi-cycle blasting through the surrounding rock from top to bottom， and finally the central pilot hole is formed.