Abstract: Abstract: In order to avoid mutually sheltered between potted-seedlings leaves and improve the light receiving environment of potted-seedlings' photosynthesis, the orientation of potted-seedlings leaves need to be adjusted to the same direction when potted-seedlings are transplanting. The orientation adjustment method of potted-seedlings leaves was presented using monocular vision while the perpendicularity and height detection of potted-seedlings had been completed using monocular vision at the early stage of the research work. First of all, the video of potted-seedlings rotating 360° was captured by an industrial camera on its side. 45 key frame images were extracted from the video at intervals of 8°, and were used as the target object. Each of extracted key frame images were processed by an 8-bit image gray-scale transformation, and image threshold segmentation of threshold 114, and image thinning. If only one pixel gray value was identical to the center pixel gray value in an 8 neighborhood of center pixels, the center pixel was determined to be the potted-seedling leaves' ending point (interest points) after their image was processed. Then, the path tracking problem of interest points were simplified to a near location shifting maximum similarity search problem using a smooth similarity function. If there are multiple interest points targeted in a close location, tracking objects were filtered through the coherence of the motion vector direction and speed using a minimizing function. If the displacement of the same interest point between two frames was larger than the preset value, the phantom points were created instead of lost interest points by a minimized near coherence phantom point function. The potted-seedling leaves' track path and corresponding directions of interest points were obtained according to the method. Finally, it was used as the target object for a pair of interest points existing x coordinate maximum values in a camera imaging plane during the course of potted-seedlings rotating 360°. The adjustment rotation angle θ of potted-seedling leaves was determined by the current location of another interest point using an inverse trigonometric formula, when one of interest points was at the maximumcoordinate position. A potted-seedling ejector was driven to revolve θ/2 by electric motor, and the orientation of the potted-seedlings leaves were adjusted the same direction with x, and the adjustment operation of the potted-seedling leaves was completed. Experiment results showed that minimum leaves adjustment direction deviation of 50 potted-seedlings was 1.51°, and the maximum deviation was 25.31°, and the percentage of the adjustment direction deviation less than 15° were 94%. Therefore, this method can meet the requirements of seedlings leaves' adjustment direction for potted-seedling transplanting.