In the project planning process of large corporations, multiple departments typically collaborate to develop strategic plans. This process can generally be simplified as follows: the upper-level decision-making department communicates strategic objectives and requirements to subsidiaries or construction units. The bi-level departments, based on their capabilities and specific needs, propose their respective project portfolios, which are then submitted to the upper-level decision-makers for review. The upper-level decision-makers adjust and optimize the overall portfolio based on the proposed plans. This decision-making process is more complex than those described in previous research but is more aligned with practical realities. Additionally, there exist interactions among projects, which may influence their returns and overall outcomes. This paper also models and describes these interrelationships. Furthermore, an algorithm is proposed to solve the problem. Finally, through a case study, the effectiveness of the proposed method is validated.