Micro-nano particles, such as micro-nano bubbles, colloidal particles, and microorganisms, exist widely in daily life and the natural environment. Observations of the dynamic behavior of such particles and their accurate quantitative characterization can enlighten us on the many core issues in life sciences, medicine, material, and environmental science. This paper introduces a digital holographic microscopy technology that can perform real-time, large depth-of-field, unmarked, high-precision three-dimensional tracking of multiple particles. Additionally, this paper expounds the working principle and application of the method and finally discusses its prospects in the further development and challenges faced by similar technologies.