Design optimization tools play an important role in improving the product quality and shortening the research and development cycle. However, most of the existing design optimization software has a steep learning curve for users and lacks state-of-the-art algorithms. To deal with this issue, we developed a cloud-based data-driven design optimization system, named DADOS. The aim of DADOS is to help engineers and researchers improve a design or product easily and efficiently. DADOS has over 30 key algorithms, including design of experiments, surrogate models, error analysis, prediction, optimization, and sensitivity analysis, which are fundamental for users to conduct design optimization. Moreover, DADOS is very flexible for expanding, it allows experts to upload their in-house code. To improve ease of use, DADOS provides a user-friendly graphical user interface and employed Flow-Based Programming (FBP) so that users don’t need to write a single code to conduct performance prediction, optimization, and sensitivity analysis. Just by dragging, dropping, and connecting algorithm blocks, they can get those jobs done. In addition, DADOS allows users to visualize the results to gain more insights into the optimization. Generally, an engineering project needs many people to complete. Thus, DADOS allows multi-person collaborating on a project at the same time and supports multi-disciplinary optimization. Since DADOS is a cloud-based system, there is no need to download and install it, users can apply it via a web browser at any time, any place, and for free, as long as they can be linked to the internet. DADOS is now available at www.dados.com.cn.