The invention discloses a double-guide-pipe underwater concrete grouting method for an ultra-large diameter pressure bearing pile. The method is characterized by comprising the following steps that a, one type of underwater self-compacting concrete is researched and developed, the slump of the underwater self-compacting concrete is 280 mm, the extended degree is 750 mm, the gradual loss of two hours is zero, and the initial setting time reaches 10 h+/-2 h; b, a type of large-volume concrete hopper is designed, an oblique panel is correspondingly arranged at the lower end of each vertical panel of the large-volume concrete hopper, and a discharging port is formed by the lower ends of the four oblique panels; c, a well mouth rack is arranged at the position of a pile opening, and two guide pipes are arranged on the well mouth rack side by side; d, the underwater self-compacting concrete is prepared in a concrete mixing plant, and the prepared underwater self-compacting concrete is transported to a construction site; and e, the conveyed underwater self-compacting concrete is poured in two large-volume concrete hoppers. By means of the method, ultra-large-diameter pressure bearing pile concrete grouting can be well finished, and the grouting quality is high.