The invention provides a probe array for an on-line dynamic train wheel set flaw detection device. The probe array is arranged between a carrying rail and a guard rail of a train forward direction detection area, and comprises a large-angle inclined probe array and a double-crystal straight probe array, wherein the large-angle inclined probe array consists of large-angle inclined probes; the double-crystal straight probe array consists of double-crystal straight probes. By arranging offset probes in the large-angle inclined probe array and distributing the probes in the double-crystal straight probe array in the direction parallel to the track direction in a staggered manner, the probe array can be subjected to crossed overlapped detection, so that the complete coverage detection of the whole wheel is effectively realized, the detectability of different types of defects at a same position is improved, and the detection accuracy and the detection efficiency are improved. Meanwhile, the probe array has the characteristics of simple structure and convenience in use, and is suitable for popularization and application.