Prefabrication is considered as a modern method of construction, transferring part of on-site work into factories and generating a new decoupling point in supply chain. Management of prefabricated component (PC) suppliers plays a key role in the performance of prefabricated construction project (PCP). Evaluating and improving supplier management maturity (SMM) become critical issues for large contractors. Previous research on PCP supply chain mainly focused on technology, process and performance aspects, while paying little attention to supplier relationship management. This study proposes an assessment criteria system of supplier management from five dimensions, including procurement process, operation efficiency, relationship coordination and strategy alignment and corporate social responsibility. A maturity grid with five levels is designed to present continuous improvement of supplier management. 34 large PCP construction firms listed in contractor directory were investigated in China through semi-structured interview and questionnaire survey. Independent two-samples t-test and one-way analysis of variance were adopted to explore SMM of different groups according to business scope, procurement method and construction experience. The results indicate that the overall maturity level of supplier management is relatively low, implying that supply activity cannot achieve inter-organization integration. Management on relationship coordination and strategy alignment lag behind procurement management and operation efficiency. Single business contractors have higher SMM than diversified ones. Contractors integrated in engineering, procurement and construction are superior to design-bid-build contractors in supplier management, especially in relationship coordination and strategic alignment. Construction experience is conductive to supplier operation efficiency. Noticeably, there are no statistically significant differences in the performance of corporate social responsibility among different groups. These results will contribute to developing a benchmark framework for contractors to evaluate SMM and achieve continuous improvements in PCP.