[RAO, Xiuqin 饶秀勤, LIN, Yangyang 林洋洋, ZHANG, Yanning 张延宁, ZHANG, Xiaomin 张小敏, YING, Yibin 应义斌, YANG, Haitao 杨海涛, JIANG, Haiyi 姜海益, ZHU, Yihang 朱逸航] NO.866 Yuhangtang Road 中国浙江省杭州市西湖区余杭塘路866号, Zhejiang 310058Xihu DistrictHangzhou, Zhejiang 310058 A method for detecting a field navigation line after ridge closing of crops. The method comprises the following steps: acquiring a field crop image; respectively performing image color spatial transformation, image binarization, longitudinal integration, neighborhood setting and regional integration calculation on the field crop image so as to obtain a crop row image; detecting an initial middle ridge, a left ridge and a right ridge in the crop row image, so as to obtain central lines of the initial middle ridge, the left ridge and the right ridge; establishing a left (right) crop row central line by using a 1 region between the central line of the left (right) ridge and the central line of the initial middle ridge; and then establishing, by using a 0 region between the left crop row central line and the right crop row central line, a middle ridge central line model to serve as a navigation line of a field operation machine. In the method, navigation information is extracted by using the difference between regional integration of a field crop image, such that detection between closed crop rows is realized.