In this study, a Cu(I) complex luminescent material Cu-P-Spiro2N with thermally activated delayed fluorescence (TADF) properties was successfully designed by combining the donor-acceptor (D-A) type ligand 10-phenyl-10H-spiro[acridine-9,9'-(4,5-diazafluorene)] (Spiro2N) with long afterglow emission properties and the auxiliary phosphine ligand bis(2-diphenylphosphinophenyl) ether (POP). The molecular structures of the Cu(I) complex were confirmed by nuclear magnetic resonance spectroscopy, and the crystal structure of the Cu-P-Spiro2N complex was further characterized by X-ray single crystal diffraction. Cu-P-Spiro2N belongs to the triclinic crystal system with cell parameters α=90.14(2)°, β=115.43(3)°, γ=115.55(3)°, a=15.10(6) nm, b=15.15(4) nm, c=16.62(6) nm. Due to the two mutually orthogonal π-conjugated planar structures of the ligand molecule Spiro2N, its highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are well separated, but with a relatively large singlet-triplet energy gap (∆E_ST). After coordination of the metal Cu(I) fragment with the ligand Spiro2N, the energy gap between HOMO and LUMO is further reduced, and the charge transfer (CT) state energy level is further lowered, which makes the complex Cu-P-Spiro2N have a very small ∆E_ST of 0.05 eV. The small ∆E_ST facilitates the reverse intersystem crossing process, thereby achieving TADF emission. The emission of this complex mainly comes from the D-A ligand Spiro2N, which exhibits metal perturbation intramolecular ligand charge transfer (ILCT) properties. At room temperature, in the doped polymethylmethacrylate (PMMA) film (10% (w)), the Cu-P-Spiro2N complex exhibits strong yellow light emission with an emission peak at 551 nm, a photoluminescence quantum efficiency of 49%, and an excited state lifetime of 6.3 μs. The results of this study indicate that by coordinating with Cu(I) ions, the excited state energy level of the ligand molecule can be modulated, reducing ∆E_ST and thus achieving TADF emission.