The invention discloses an expanded excavation region hole inside and outside combined delayed regional differential blasting network in tunnel blasting. The network is characterized in that blasting excavation is performed by using a three-step method for an underground excavated metro interval tunnel underneath passing historical and cultural relic buildings; longitudinally excavating along the tunnel to form an upper step, a middle step and a lower step in sequence; arranging the expanded excavation region hole inside and outside combined delayed regional differential blasting network, i.e., dividing an upper step expanded excavation region according to upper, middle, lower, left and right structures, forming synchronous blasting sections in two to four adjacent blast holes in each divided region by using an identical section detonator, and blasting section by section by using detonators of different sections between different synchronous blasting sections. The network can guarantee that the blasting vibration viscosity of the construction section underneath passing the historical and cultural relic buildings meets the related requirements, the historical and cultural relic buildings are protected from being damaged, and the construction progress is guaranteed.