The invention discloses a complicated supporting construction method of a passage passing through a box culvert. The complicated supporting construction method of the passage passing through the box culvert comprises the steps of excavating covering soil at the top and the left and right external side w of the box culvert to the bottom wall of the box culvert according to a set position of the passage passing through the box culvert so as to to form a foundation pit; correspondingly arranging three right side manual digging filling piles and a left side manual digging filling pile on the rightand left side walls of the box culvert in sequence; grouting in a soil body between the manual digging filling piles on the right and left sides; continuing to cut through and excavate downwards fromthe right side of the bottom wall of the foundation pit to the left side of the bottom wall of the foundation pit; erecting a scaffold at the same time of excavating in the excavating process; erecting three steel pipe supporting columns in the middle of the bottom wall of the box culvert; correspondingly building pedestrian passageway side walls on the two sides of a construction passage; pouring a pedestrian passageway top plate at the top of a pedestrian passageway; and blocking a hole in the pedestrian passageway top plate in the corresponding position of each steel pipe supporting column. According to the complicated supporting construction method of the passage passing through the box culvert, the excavating safety and the passage main body construction structure safety are guaranteed.