With the development of deep learning, the application of automatic road extraction has achieved great success. However, the main challenge is how to make full use of a large number of unlabeled images to improve segmentation models and how alleviate sample imbalance in road extraction tasks. In this paper, we propose a novel semi-supervised remote sensing road extraction approach is refined as Foreground Mixup into Weighted Dual-network Cross Training (FMWDCT), which combines labeled images with unlabeled images to extract road from remote sensing images. FMWDCT is composed of Dualnetwork Cross Training (DCT) and Foreground Pasting (FP). DCT is a new semi-supervised training method and FP is an effective data perturbation method for road extraction. We firstly paste the foreground pixels obtained from labeled images into unlabeled images to produce mixed input images. The mixed pseudo labels are then generated by a combination of highconfidence predictions from the augmented network and labeled masks. Finally, the mixed pseudo labels are used to guide another adversarial basic network for cross training, and this basic network is used to smoothly update the augmented network that corresponds to it. The proposed FMWDCT effectively solve the overfitting problem and imbalance problem of positive and negative sample in the case of a few labeled training samples. We demonstrate the effectiveness of our method on three road extraction datasets, and achieve better performance with few labeled data. Extensive experiments show that the proposed semi-supervised method can learn latent information from the unlabeled data to improve performance.