Offshore wind turbines are being deployed at an unprecedented scale, mainly driven by China, to combat the global climate crisis. However, these wind turbines are highly material-intensive, which has aroused wide concerns on potential supply risks and end-of-life material decommissioning and management. Here, we develop an integrated Energy Infrastructure-Material Stock monitoring approach of offshore wind turbines (EIMS_owt) using satellite images to quantify the in-use stock of components (rotor, nacelle, tower, and cable) and materials (bulk metals, rare earth, and others) for each turbine unit in China. We captured the installment and operational data of nearly all existing offshore wind turbines and witnessed a 22-fold increase from 267 turbines in 2015 to 5921 turbines by 2022. Meanwhile, we find that over two-thirds of those turbines, associated with 4.5 million tons (Mt) of critical components such as rotors and nacelles in 2022, are located at offshore distance exceeding 20 kilometers, posing large challenges for their operation and waste management. It is estimated that around 3.5 Mt of steel, 157 kilotons (kt) of copper, 41 kt of aluminum, and 2.3 kt of rare earth are contained in those components, highlighting the prospective value of their future recycling. Accordingly, our approach provides a high-resolution and up-to-date monitoring solution to help both China and other countries in improving sustainable performance of their wind energy infrastructure.