The invention discloses a wheel steering angle measuring device and measuring method of a broken trapezoidal steering system. The wheel steering angle measuring device comprises a steering angle sensor, a connecting sleeve and a stopping block, wherein one end of the connecting sleeve is fixedly connected with a housing of the steering angle sensor; a central shaft of the steering angle sensor is located in the connecting sleeve; the stopping block is fixed to the central shaft of the steering angle sensor through a pin column; during mounting and use, the other end of the connecting sleeve is fixedly connected with a left swing arm of the steering system; the stopping block is clamped in a stopping hole formed along the axis of a vertical shaft of the left swing arm; and the wheel steering angle measuring device has the advantages of being simple in structure, convenient to use and accurate in measurement. The measuring method comprises the following steps of measuring a steering angle of the left swing arm in real time by the steering angle sensor; calculating a steering angle of a left wheel in real time by a space mechanism method according to the steering angle of the left swing arm measured in real time; and according to the steering angle of the left swing arm measured in real time, calculating a steering angle of a right wheel in real time by the space mechanism method. The measuring method has the advantages of being high in real-time performance and high in reliability.