Abstract: Steering radius is an important index to study the steering characteristics of agricultural machinery. At present, the commonly used measurement methods have some disadvantages, such as large limitations, complex operation, high price and so on. Therefore, this paper designs a method to measure the steering radius of agricultural machinery based on machine vision. By placing a benchmark in the test site and installing a camera on the agricultural machinery, when the agricultural machinery moves, record the image of a specific point on the benchmark, and calculate the steering radius at a certain time by reading the image information. Beidou navigation system is used to verify and improve the results of this method. The final measurement error is less than 10cm, which meets the accuracy requirements of field experiment. The operation steps of this method are divided into calibration, camera, image processing and calculation. Most of the time is completed indoors, which can greatly reduce the time and intensity of field work. It has the advantages of simple operation and low cost. It can be applied to the measurement of steering characteristics of agricultural machinery.