The invention provides a high-precision wheel turning angle measuring device and measuring method. The high-precision wheel turning angle measuring device is used for an agricultural machine automatic navigation control system and is simple in structure and easy to mount. The measuring device comprises a connecting rod structure, a collecting module and an angle sensor. the connecting rod mechanism is connected with an agricultural machine steering mechanism, and the linear motion of an agricultural machine steering oil cylinder is transformed into the rotation of the angle sensor, or the swing of an agricultural steering arm is transformed into the rotation of the angle sensor; a 32-bit embedded processor serves as a kernel of the collecting module, and the collecting module is provided with various angle sensor data collecting interfaces. According to the measuring method, original data of the angle sensors are transformed into wheel turning angle values according to a model of the relation between wheel turning angles and output values of the angle sensor. According to the wheel turning angle measuring device and measuring method, mechanism and measurement integrated design is achieved, and the wheel turning angle measuring device and measuring method are novel for the agricultural automatic navigation control system.