BrainNet Viewer is a MATLAB-based toolbox for visualizing human brain connectomes as ball-and-stick models. It allows researchers to load various file types, including brain surface, node, edge, and volume files, to display different combinations of brain networks. The toolbox includes an intuitive settings panel for adjusting display properties such as color, size, and layout. It also supports interaction functions for detailed information display and can export figures as common image formats or videos. BrainNet Viewer is freely available on the NITRC website and is designed to be user-friendly, flexible, and efficient for visualizing brain networks. It provides functions for volume-to-surface mapping, ROI cluster construction, and network analysis. The toolbox has been tested on multiple operating systems and is compatible with Windows, Linux, and Mac OS. It is used to visualize functional brain networks derived from resting-state fMRI data, revealing topological properties such as hubs, modules, and connectivity strengths. BrainNet Viewer offers a range of visualization options, including different layouts, color mappings, and interactive features. It supports batch processing and command-line operations for generating network figures and videos. The software is compatible with other brain connectome analysis toolboxes and provides a platform for exploring the topological organization of brain networks. Despite its advantages, BrainNet Viewer faces challenges such as high memory consumption and slow processing for large networks. Future improvements include enhancing user experience, adding automatic label placement, and expanding visualization capabilities. BrainNet Viewer is a valuable tool for brain connectome studies, offering a flexible and efficient platform for visualizing and analyzing brain networks.BrainNet Viewer is a MATLAB-based toolbox for visualizing human brain connectomes as ball-and-stick models. It allows researchers to load various file types, including brain surface, node, edge, and volume files, to display different combinations of brain networks. The toolbox includes an intuitive settings panel for adjusting display properties such as color, size, and layout. It also supports interaction functions for detailed information display and can export figures as common image formats or videos. BrainNet Viewer is freely available on the NITRC website and is designed to be user-friendly, flexible, and efficient for visualizing brain networks. It provides functions for volume-to-surface mapping, ROI cluster construction, and network analysis. The toolbox has been tested on multiple operating systems and is compatible with Windows, Linux, and Mac OS. It is used to visualize functional brain networks derived from resting-state fMRI data, revealing topological properties such as hubs, modules, and connectivity strengths. BrainNet Viewer offers a range of visualization options, including different layouts, color mappings, and interactive features. It supports batch processing and command-line operations for generating network figures and videos. The software is compatible with other brain connectome analysis toolboxes and provides a platform for exploring the topological organization of brain networks. Despite its advantages, BrainNet Viewer faces challenges such as high memory consumption and slow processing for large networks. Future improvements include enhancing user experience, adding automatic label placement, and expanding visualization capabilities. BrainNet Viewer is a valuable tool for brain connectome studies, offering a flexible and efficient platform for visualizing and analyzing brain networks.