Complex systems involve a wide range of areas, including nature, engineering, biology, economy, management, politics, and society. The complex phenomena it explores range from the life phenomenon presented by a cell, to the fluctuation of the stock market, the management of urban traffic, the prediction of natural disasters, and even the rise and fall of society. At present, the study of complexity has been widely concerned by scientists from all over the world.

In recent years, with the continuous development of financial innovation, the volatility of the financial market is increasingly intensified, and the interaction between the markets is increasing day by day. Since Markowitz founded portfolio theory, the problem of risk management and investment decision-making has been paid more and more attention and in-depth studied by economists all over the world. Compared with the traditional normal distribution hypothesis, the financial time series often presents temporal, skewed, spike, thick tail, and asymmetric fractal characteristics, and has a nonlinear complex dependent structure. Therefore, how to accurately describe the risk of an asset portfolio is of great practical significance for investors and asset managers.

This Special Issue aims to collate cross-disciplinary original research and review articles with a main focus on the laws of natural, socio-economic, and financial complex systems. These will include not only new models, algorithms, and innovative applications, but also practical solutions that how to tailor generic approaches to natural and social systems.

Potential topics include but are not limited to the following:

• Multi-scale fractal theory
• Complex network analysis
• Financial support for emergency rescue
• Complexity of financial system
• Enterprise innovation and management
• Disaster complexity
• Evolution of ecosystem
• Management theory and method based on Complexity Science
• Data mining and evolutionary computing method