Abstract: Abstract: Intra-row mechanical weeding technique and device can free strenuous labor and eliminate the detriment of using chemical weed. The yaw error is barely avoidable when running a tracked crop-row tractor. It can result in an inconstant side-shift between the intra-row mechanical weed device and crop row and the increasing of crop damage and untreated weeds in intra-row area. The objective of this research is to develop a crop row tracking control algorithm for the optimized measurement of side-shift offset. The crop row line is obtained by using least square fit from 20 crops in several consecutive images, and the side-shift offset is estimated based on weeding device lateral position to keep a constant distance between the weeding device and crop row. Then, the PD control algorithm with bi-threshold dead band for transverse controller is developed to reduce the transverse error when the estimated offset exceeds the dead band. It needs to be ensured that the origin of the weeding device follows the desired route and parallels the crop row, by controlling velocity and direction of DC motor. The test results prove the good performance of standardized signal tracking using sine wave and triangle wave. The maximum and average sine wave tracking error is 10 mm and 0.8 mm, respectively, with a forward velocity of 0.2 m/s. The maximum and average triangle wave tracking error is 11 mm and 1.2 mm, respectively, with a forward velocity of 0.5 m/s. The results from weeding experiment in soil bin indicate that the side-shift enabled control of the transverse position of the weeding device and is able to follow the crop row line with an accuracy of ±13.4 mm at 0.2 m/s and ±20.8 mm at 0.5 m/s forward velocity. The untreated weeds in the intra-row area decreased significantly. The treated intra-row area achieve up to 93.3 % and 85.9 % of field surface for a mean plant spacing of 300 mm and 200 mm, respectively. The danger of crop damage is significantly reduced by using side-shift control. Compared to the rate of crop damage up to 20% without using the transverse controller, the rate of crop damage is down to less than 12% by using the side-shift control. The accuracy of intra-row weeding device tracking is high and acceptable.