Abstract: In order to improve the detection efficiency of rail flaw detection, the rail flaw detection vehicle for heavy haul railway based on fast phased array technology was developed, and the rail flaw detection of heavy haul railway at 80 km ·h^-1 speed was realized. The system can detect 276 artificial damages at the rail head, rail waist and rail bottom at the speed of up to 80 km ·h^-1 under the conditions of 60 kg ·m^-1 rail (referred to as 60 rail for short) and 75 kg ·m^-1 rail (referred to as 75 rail for short) calibration line. The average detection rate of the damage was 90. 7% and 91. 2% respectively. At the same time, the A-scan signal amplitude of the defect was more than 100%, and the signal-to-noise ratio was more than 24 dB, which meets the detection requirements of relevant standards. Through flaw detection at a speed higher than 60 km ·h^-1 on the main line, the accumulated mileage of flaw detection has exceeded 2 500 km, and one case of railhead transverse crack was found, which is consistent with the result rechecked by GTC-8C digital rail flaw detector. In addition, the typical characteristics of 30 section lines were tracked, and the B-scan pattern has good repeatability and high consistency with GTC-8C digital rail flaw detector, which preliminarily verifies the detection effect of the phased array flaw detector at different speeds and different line conditions.