IR scholars have formed two major camps of"Structural Determinism"and"Agent Determinism",based on their attitude about the relationship between systems and actors.This paper proposes a theoretical framework of weak structural realism,aiming to rethink the relationship between structure and agent.Weak structural realism rejects both the absolute structural choice of structural realism and the absolute agent choice of various reductionist theories,instead attempting to find a third way.As a variant of structural real-ism,weak structural realism develops its theory while adhering to a series of basic assump-tions of structural realism(except that states are rational actors).It argues that systems can only drive actors through structural pressure,which is a variable rather than a constant.Changes in structural pressure stem from changes in state interactions,meaning that struc-tural pressure is shaped by interstate interactions.In this way,weak structural realism re-habilitates the agency of actors and forms a model of bidirectional interaction between sys-tems and actors.Compared with structural realism,weak structural realism can better ex-plain and predict changes in states'foreign policies and interstate relations over longer peri-ods.Compared with various reductionist theories,it can help us better understand the over-all trends in the development of great power relations over longer periods.The policy value of weak structural realism lies in its opposition to the deterministic judgement of structural realism,especially offensive realism,which regards the politics of great powers as a trage-dy,as well as to the wishful inference of various reductionist theories,especially grand strategy theories,which hope that individuals or groups can reverse the tragic essence of great power politics in one fell swoop.