As one of the key ground-based facilities of the Chinese–French Space-based multi-band Variable Objects Monitor (SVOM) mission, the main scientific objectives of the Ground-based Wide Angle Camera array (GWAC) are to detect prompt optical emission of gamma-ray bursts or other short duration astronomical transients on a second-scale temporal resolution. GWAC is located at Xinglong Observatory, China, and consists of 10 mounts and 40 cameras, providing a joint field of view of about 3600 square degrees. The detection ability is 16 mag in 10 s of exposure time in the visual band under the condition of the new moon phase. Here, we give an overview of GWAC and introduce the science motivation of the project, as well as the performance of the hardware and the software. The observation strategies and the data processing are briefly presented. The early sciences in the last 5 yr since the first light are summarized.