In recent years, with the development of artificial intelligence, algorithmic empowerment has gradually become an important driving force for the high-quality development of the social assistance system. This study is devoted to grasping the underlying operational logic of algorithm-enabled social assistance decision-making from the perspective of instrumental rationality and value rationality, deeply analyzing the risk of alienation it may induce, and finding targeted optimization strategies. It finds that algorithms empower social assistance decision-making through the internal logic of perceived demand, resource allocation, and collaborative governance, and realize the explicitation of implicit demand, the precision of resource allocation, and the coordination of governance actions. However, while improving governance efficiency and enhancing the precision of social assistance, algorithms also give rise to tension between technical logic and public value: first, at the technical level, the algorithmic black box obscures procedural justice, that is, the decision-making process is low in transparency and difficult to explain; second, it is the vacuum in the regulatory field caused by the ambiguity of the boundary of power and responsibility at the institutional level, that is, it is difficult to clarify the responsibility of algorithm developers and grass-roots staff when decision-making is wrong; third, the excessive expansion of instrumental rationality at the value level dispels the subject status of recipients and even triggers a new type of digital exclusion. To solve the above dilemma, this study constructs the governance logic of the trinity of technology, system, and value, reshapes the technical trust by constructing an interpretable and auditable algorithm mechanism, anchors the power and responsibility of human-machine coordination based on the whole chain accountability system, and promotes the return of technical rationality to humanistic value, aiming to provide references for the unity of efficiency improvement and value persistence of the social assistance system in the digital age.