The promotion of technical and management capabilities is one of the important strategies in government policy to enhance the competitiveness of small and medium enterprises (SMEs). A serial of efficient and accurate decision-making models is then required to achieve this strategic goal. The construction machinery industry belongs to SMEs. It is also essential for infrastructure construction in Taiwan. This study aims to show the ways to improve the performance of SMEs in an uncertain environment. To deal with this issue, the Fuzzy Delphi method and fuzzy analytic hierarchy process (FAHP) are used to find key success factors (KSFs) of SMEs. TOPSIS method is used to find the best project leader for their projects. Also, the MCGP-U method is used to find the optimal resource allocations. In addition, the “plan-do-check-action cycle” is used to emphasize the importance of sustainable improvement. The contributions of the proposed model are as follows: (1) it considers multi-faceted of SMEs to avoid wrong decisions; (2) it can easily obtain the SEM’s KSFs to improve the performance of SMEs; and (3) the results of the study can be used to improve SEMs' managerial fitness and effectiveness.