Abstract: Fermented milk has a long history of being fermented by lactic acid bacteria. Fermented milk contains many elements, including protein, minerals, and vitamins. Fermented milk is gaining more and more attention from customers as people’s desire for a high quality of life improves. Most of the fermented milk on the market today are prepared with single strains or traditional lactic acid bacteria (Streptococcus thermophilus and Lactobacillus bulgaricus) as fermenting agents. However, this production method results in issues like an excessively long fermentation time, a mildly inferior taste, and poor stability. Compound strains have recently gained attention in the field of fermented milk preparation. By utilizing interactions and synergies between various strains, it is possible to increase the quantity and diversity of metabolites, enhancing the quality and functional properties of fermented milk and compensating for some of the shortcomings of conventional fermented milk in terms of product morphology and sensory experience. This study examines how complexing strains have accelerated pH reduction, improved the product’s sensory qualities, rheological characteristics, and water-holding capacity, as well as increased their capacity for lipid-lowering, anti-inflammatory, antioxidant, and bacteriostatic effects. Finally, the future research paths for fermented milk innovation are intended to offer suggestions for the diverse, functionalized, and precise production of fermented milk.