Heterostructure engineering for sulfur hosts is an effective way to achieve interfacial synergistic effects on suppressing the "shuttle effect" of polysulfides and thus improve electrochemical performance of lithium–sulfur (Li–S) batteries. Rational selection and design of different components into heterostructures is vital to enhance the synergistic effect. Herein, MoS₂/MoP Mott–Schottky heterostructure nanoparticles decorated on reduced graphene oxide (MoS₂/MoP@rGO) are fabricated and used as sulfur host firstly. Theoretical calculation and experiment results reveal that the in-situ introduction of MoP could tune the electronic structure, activate the basal plane of MoS₂, and achieve the interfacial synergistic effects between adsorption (MoS₂) and fast conversion (MoP). Such synergistic effects enable MoS₂/MoP@rGO to not only remarkably facilitate Li₂S deposition during the discharging process but also significantly accelerate the Li₂S dissolution during the charging process, demonstrating bidirectional promotion behaviors. Thus, the designed cathode delivers initial capacity of 919.5 mA∙h∙g⁻¹ with capacity of 502.3 mA∙h∙g⁻¹ remaining after 700 cycles at 0.5 C. Even under higher sulfur loading of 4.31 mg∙cm⁻² and lower electrolyte to sulfur (E/S) ratio of 8.21 μL∙mg⁻¹, the MoS₂/MoP@rGO@S cathode could still achieve good capacity and cycle stability. This work provides a novel and efficient structural design strategy of sulfur hosts for high-performance Li–S energy storage systems.