Electroslag remelting (ESR) is an important metallurgical process for producing high-purity materials with homogeneous compositions and sound microstructures, and its typical products are ingots or simple castings. The core principle involves the resistive melting of a consumable electrode within a slag pool, followed by the refining of molten metal droplets as they traverse the slag, and subsequent sequential solidification in a water-cooled mold. However, conventional ESR processes face limitations in producing large or complex-shaped components, enhancing production efficiency, achieving highly specialized microstructures, and meeting ultra-high purity demands for advanced applications. Advanced composite ESR technologies have been developed to overcome these limitations by innovatively modifying key process aspects. For instance, electrode systems are improved using vibration, rotation, or multiple electrodes. Enhanced mold design and solidification control are achieved through techniques including conductive molds, mold rotation, and ingot withdrawal. Precise control of the process is realized through the use of protective gas, vacuum, or elevated pressure, as well as the application of external fields such as magnetic fields or ultrasonic vibration. This review comprehensively summarizes these advanced techniques, examining their principles and characteristics, and discussing their specific advantages and challenges.