Abstract: Droplet icing is a common phenomenon in various aspects of our daily life and industrial applications. Understanding the process of droplet icing is of great importance in fields such as aviation safety, wind power generation, and the design of polar marine equipment. Optical measurement methods provide an important and non-contact approach for investigating the process of droplet icing. This review aims to comprehensively summarize and evaluate commonly employed optical measurement methods in droplet icing research. By providing an in-depth analysis and comprehensive perspective, it seeks to enhance our understanding of optical measurement techniques in droplet icing experiments. The review begins by summarizing the key physical processes and mechanisms involved in droplet icing, emphasizing their importance in studying this phenomenon. It subsequently classifies and introduces commonly utilized optical measurement methods in droplet icing research. These methods include traditional optical microscopy, high-speed photography, incoherent optics, laser detection techniques, and advanced optical technologies that have emerged in recent years. By analyzing the principles, advantages, disadvantages, and application cases of each method, we point out that optical measurement methods play a crucial role in visualizing and revealing the microscopic details, dynamic processes, and underlying mechanisms of droplet icing. However, this review also acknowledges the challenges faced by these methods, such as limitations in spatiotemporal resolution, measurement accuracy, and interference suppression. With the hope that optical measurement methods can provide more powerful support for researches and applications in related fields, the review also identifies areas for improvement and discusses potential advancements to enhance the capabilities of optical measurement techniques. It discusses potential strategies for improving resolution, sensitivity, accuracy, and comprehensiveness of optical measurements. Additionally, it also explores the potential integration of machine learning to enhance optical measurement technology. The ultimate goal is to facilitate scientific research and engineering applications in fields impacted by droplet icing through the continued development and utilization of optical measurement methods.