The invention discloses a train wheel combined ultrasonic flaw detection device which comprises a probe carrier, wherein the probe carrier is divided into a plurality of smaller sub-carriers; all the sub-carriers are independently mounted, work in a combined form and are arranged on the same circumference of the wheel tread. In the invention, the size of each sub-carriers is reduced, so that the sub-carriers can enter into a narrow space at the train bottom, can effectively avoid the barriers at the train bottom, can match the wheel flaw detection checking surface perfectly, such as the tread, can perform comprehensive combined flaw detection on the rim and spoke of the whole wheel and can meet the environment requirement for the space at the bottom of various trains.