As a closed space with high-density crowds, the emergency evacuation efficiency of subway buildings under sudden fires and other incidents is highly dependent on the dynamic interaction between individual and group behaviors. Traditional social force models are mostly based on the assumption of individual independence, and it is difficult to describe the common companion behavior and its asymmetric information transmission mechanism in reality. To address this issue, an improved social force model that integrates the characteristics of companion behavior is proposed: introducing the relative weight attraction mechanism to describe the asymmetric relationship of "guidance-following" in loose companion groups with leaders, and adding the speed synchronization term to enhance group cohesion; The Morse potential function is used to describe the nonlinear attraction-repulsion effects within a close-companion group, which more realistically reflects the dynamic behavior of a family or acquaintance team. On this basis, a three-dimensional simulation scenario of a typical island subway station is constructed, and the influence of the number of exits and obstacle types (turnstiles, security checkpoints) on the evacuation efficiency is systematically explored. Simulation experiments show that increasing the number of exits can significantly shorten the evacuation time, but it needs to be cooperated with physical point obstacles. The results not only provide a more realistic companion modeling framework for emergency evacuation simulations in subway construction, but also offer theoretical support and practical basis for the optimization of evacuation strategy, corridor design, and the development of crowd guidance strategies.