Traditional solvent-based polyurethane (PU) releases a significant amount of VOCs during production and use, posing a threat to human health and the environment, making it increasingly unsuitable for industrial standards. In contrast, solvent-free polyurethane (SFPU) has attracted considerable attention in recent years due to its environmentally friendly nature, low energy consumption, and high thermal stability. Therefore, a systematic elucidation of the impact mechanism by functional modification on SFPU is crucial for guiding the complex design of SFPU for specific application conditions. SFPU are generally divided into two types: two-component system (2K-PU) and single-component system. Although single component system can be used without curing, two component system exhibits higher bonding strength and durability, making it suitable for high-standard applications. The main modification methods, research progress of solvent-free two-component polyurethane both domestically and internationally are reviewed. The main modification methods of 2K-PU in different material applications are analyzed emphatically, including functional filler modification and chemical intrinsic modification. Finally, some urgent application problems of 2K-PU are prospected. It is pointed out that modern polyurethane system is still based to some extent on petrochemical materials, while the market prospect for solvent-free polyurethane is clear.