Abstract: High slip rate will reduce the efficiency of tractor operation. Therefore, it was of great significance to accurately monitor the slip rate. Aiming at the problem that the method of measuring the slip rate at the minimum wheel speed was fails under steering conditions, a sliding rate measurement method based on the Ackerman steering principle was proposed. By establishing the slip rate measurement model during steering, the relationship between slip rate and the theoretical vehicle speed, the vehicle speed and steering angle of the right front wheel was obtained. Based on the John Deere 4720 tractor, the slip rate measurement system was designed, including the speed measurement device of the right front wheel, the CAN bus analysis module and the slip rate calculation module. The slip rate measurement test was carried out in the straight driving condition of the cement pavement, and the average slip rate in the straight driving condition was 3.0%. The slip rate was measured under the steering condition of cement pavement, and the target theoretical velocities were 0.5, 0.8, 1.0, 1.2 and 1.5 m/s respectively. The test results showed that the average sliding rate in steering condition was 3.9%, 3.4%, 3.7%, 3.8%, 2.9%, respectively. The slip rate of the steering condition was in the slip rate range of the straight running condition. Therefore, it was considered that this method was feasible and provided support for the measurement of the slip rate of agricultural machinery in field steering conditions.