Driven by vegetarianism, dietary nutrition, environmental friendliness and other factors, plant-based diet, which is an alternative to animal derived foods, has developed rapidly worldwide in recent years. As an important branch, plant-based milk substitutes have received huge attention from scientific research, industry, and consumers. First, the development and research status of the plant-based milk substitutes industry both domestically and internationally was reviewed. Then, a comprehensive summary of the scientific research progress and industrial development status of plant-based milk substitutes with regard to their nutritional and functional properties, processing technology, and quality improvement was provided. The nutritional composition of cow's milk and common plant-based milk substitutes were compared and analyzed. The preliminary performance of plant-based milk substitutes in health efficacy research was presented. The key technical aspects of raw material pretreatment, grinding, enzymatic digestion, homogenization, and sterilization involved in the processing of plant-based milk substitutes and their effects on product quality were systematically summarized. The common problems, quality challenges, and improvement measures in the stability, flavor and taste, and nutritional quality of these products were discussed. Finally, some suggestions were presented for the scientific and technological innovation and future development of the industry in terms of raw material processing suitability, green and advanced processing technologies selection, and new plant-based resources mining, with a view to providing references for the sustainable development of the new industry of plant-based milk substitutes.