Overwork is a well-known issue that has drawn increasing interest. It poses significant threats to individuals, including impacts on health and economic well-being. However, due to the lack of a uniform measurement for overwork across different countries and regions over time, existing literature has produced many controversial conclusions. In recent years, nocturnal light data has been extensively used to objectively capture social and economic activities. We developed an objective and uniform overwork index, combining daily high-resolution nightlight satellite data and firm registration data from The State Administration for Industry and Commerce (SAIC) at both grid and prefecture levels in China. This index shows reasonable responsiveness and trends in relation to national and local events. This algorithm and dataset are highly adaptable and can be extended to different countries and geographic areas, providing valuable support for various studies in economics and sociology, such as labor dynamics and income distribution.