With the rapid development of the low -altitude economy，collaborative delivery involving unmanned aerial vehicles and ground vehicles has emerged as a promising approach to alleviating the “last-kilometer ” bottleneck in logistics.This paper systematically reviews the conceptual definitions，typical application scenarios，and operational modes of air -ground collaborative delivery systems，and argues that the three -dimensional coupling of time，space，and task constitutes the fundamental characteristic of such problems.Air-ground collaborative delivery systems can be classified into three operational modes：vehicle -mounted takeoff and landing，fixed handover points，and dynamic rendezvous.Correspondingly，the modeling framework has evolved through four levels，from mechanism -based benchmark models to dynamic and robust models.Solution methods have also shifted from exact approaches to hybrid optimization frameworks centered on feasibility assurance，integrating mathematical decomposition，metaheuristics，and learning -driven methods.Current research still faces several challenges，including insufficient endogenization of airspace regulatory constraints，limited adaptability to complex environments，and weak engineering deployability.Future research should promote the transition of air -ground collaborative delivery systems from theoretical optimality to stable and operationally viable deployment through hierarchical integrated modeling，endogenous representation of capacity and congestion effects，and the development of robust and online optimization mechanisms，thereby supporting their large -scale and sustainable application.