We constructed a triplet energy transfer (TET) system based on 2,2'-(4,7,11,14-tetra(benzofuran-5-yl)-1,3,8,10-tetraoxo-1,3,8,10-tetrahydroanthracene [2,1, 9-def:6,5,10-d'e'f'] diisoquinoline-2,9-diyl) diacetic acid (PBI-FN) and PbS quantum dots (QDs) with different sizes. Through steady-state and femtosecond time-resolved absorption spectra, the TET kinetics between PBI-FN ligands and PbS QDs have been investigated. At the same time, TET driving forces can be controlled by attaching PBI-FN on the surface of PbS QDs with different band gaps, which confirmed the energy dependence of the TET process. For PbS QDs with band gap of 0.91 eV, the TET process can hardly occur due to the large energy variance between the PBI-FN ligand and PbS QDs. For PbS QDs with band gaps of 1.29 and 1.45 eV, the energy transfer process from PBI-FN to PbS QDs can be successfully realized, and the corresponding time constants are 3.24 × 10⁻¹⁰ s and 1.69 × 10⁻¹⁰ s, respectively. The attenuation of various paths in the TET system is a complex photophysical process. We hope that this work will provide guidance for the design of the TET system from the perspective of dynamics.