Given a query language, a Detection-based Vision-Language Understanding (DVLU) system needs to respond based on the detected regions (i.e.,bounding boxes). With the significant advancement in object detection, DVLU has witnessed great improvements in recent years, such as Visual Question Answering (VQA) and Visual Grounding (VG). However, existing DVLU methods always process each detected image region separately but ignore that they were an integral whole. Without the full consideration of each region’s context, the image’s understanding may contain more bias. In this paper, to solve the problem, a simple yet effective Region Collaborative Network (RCN) block is proposed to bridge the gap between independent regions and the integrative DVLU task. Specifically, the Intra-Region Relations (IntraRR) inside each detected region are computed by a position-wise and channel-wise joint non-local model. Then, the Inter-Region Relations (InterRR) across all the detected regions are computed by pooling and sharing parameters with IntraRR. The proposed RCN can enhance the features of each region by using information from all other regions and guarantees the dimension consistency between input and output. The RCN is evaluated on VQA and VG, and the experimental results show that our method can significantly improve the performance of existing DVLU models.