At construction sites, subcontractors are the actual decision-making units responsible for allocating manpower. Therefore, if construction firms can effectively grasp the priority of subcontractors' manpower allocation, they can sustain their operations and development in the context of labor shortage. In this study, subcontractors were interviewed in a semi-structured manner to identify nine factors influencing their willingness to work. Accordingly, this research designed a questionnaire to investigate the willingness of the contractors to respond to the nine factors. This study discovers that the contractors are more willing to cooperate with the way of "providing rush bonuses", "ensuring smooth on-site operations", "providing free parking or solving parking problems", "establishing long-term cooperative relations" and "improving on-site welfare." Therefore, under the premise of not increasing the overall subcontracting budget, if the contractor can take the above measures with a higher willingness to cooperate, it should be easier to reduce the impact of labor shortages. Thus, this research offers a feasible shortage countermeasure for the contractors in the construction site management practice.