The invention relates to a hole distribution method for blasting demolition of a reinforced concrete support beam in a foundation pit. An arc pipe set (1) is embedded in the reinforced concrete support beam (3) in the foundation pit in the longitudinal direction; 1 or 3 arc pipes are in the arc pipe set (1); pipe ports in two ends of each arc pipe are upwards; a linear distance L between the pipe ports in two ends is 1800-2300 mm; and a center connecting line of the pipe ports in the same ends of all the arc pipes in the arc pipe set (1) is perpendicular to a long edge of the reinforced concrete support beam (3). 2 straight pipes (2) are embedded in the middle position of the arc pipe set (1); each straight pipe (2) is perpendicular to the upper plane of the reinforced concrete support beam (3); and distances from the pipe port in the upper end of each straight pipe (2) to the pipe ports in the upper ends of adjacent arc pipes on two sides are the same. The hole distribution method has the characteristics of convenience for construction, short construction period, low cost, capability of improving the safety and the reliability of blasting demolition and capability of enhancing the blasting demolition effect.