In this study, the author examined how ideas, historical contexts, implemented structure and individual factors influenced needs assessment system for the disabled and the subsequent realization of the delivery system of welfare service in Taiwan. First, Taiwan’s transition to managerialism in the face of the tension between marketization and social protection under neoliberalism is expounded. Next, the specific development process and context that Taiwan underwent when designing policies for the disabled is explained. According to the discerned historical context, this study then discusses Taiwan’s disability evaluation and needs assessment systems and changes. The following effects of institutionalization is discerned: in addition to the legal welfare and service items that contain adult-centric and ableist biases originating from the independent-dependent dichotomous concepts, the streaming system for administrative conveniency, and the legal welfare and service items adopted as the content of needs assessment, have all restricted imaginations on the subject of the disabled and their needs as well as the content of actual service delivery. Implications on related policies are provided as the conclusion of this study.