For artificial supramolecular architectures designed to mimic biological systems, achieving different pathway synthesis is challenging due to the requirement of multiple stable and interconvertible intermediates. Here, we propose a novel "inner-outer steric synergy" strategy and investigate controllable pathway engineering for the synthesis of specific structures. Firstly, three structures (Ring-Pd2LA2, Bowl-Pd2LA3 or Cage-Pd2LA4) with interconversion properties were selectively formed by assembling externally modified ligand LA with Pd(II). Furthermore, Ring-Pd2LA2 can further assemble with the ligand LB with inner steric hindrance to generate heteroleptic trans-Pd2LA2LB2 cage, while Bowl-Pd2LA3, as an intermediate, can assemble with LB to form Pd2LA3LB. It is noteworthy that Ring-Pd2LA2, Bowl-Pd2LA3, and Cage-Pd2LA4 can interconvert under specific conditions, enabling the synthesis of Pd2LA3LB and trans-Pd2LA2LB2 through 10 and 16 pathways, respectively. This research not only introduces a novel strategy for constructing heteroleptic cages but also demonstrates the achievement of pathway engineering.