Horizontal logistics collaboration is characterized by the highly professional cooperation of logistics service providers at the same level of the supply chain, which is an effective way to optimize the development and sustainability of modern logistics. Conducting a coding analysis of data from 41 in-depth interviews, this study constructs a theoretical framework of the driving force of horizontal logistics collaboration among Chinese logistics service providers to synchronously improve service, market, efficiency, and emergency competitiveness through cooperation with peer competitors to enhance sustainable comprehensive competitiveness. The four driving forces encourage logistics service providers to adjust their thoughts in the planning stage, change their behavior in the implementation stage, and transform their strategy in the evaluation stage. The results also indicate differences between China and other countries in the driving force, effective utilization of logistics workers, cross-institutional collaboration of state-owned enterprises, and integration of artificial intelligence technology. Finally, we propose relevant recommendations for managers.