A between-row weed detection method using the position feature of drilled crop was developed in this paper. The drilled crop was regularly sown as a row space, and the method of pixel lateral histogram was used to extract the centre of the crop row. Because most weed was distributed on the bare-soil zone of the crop rows, between-row weed was detected by the seed fill algorithm, which could fill the crop areas connecting with the left and right borders of each crop row. And the start point of each crop row border was set as the seed point. The experimental results showed that the mean correct classification rate of between row weed was 80%, and the mean mistake classification rate was 4.2%.