Square planar platinum (II) complexes were reported with intense electrochemiluminescence (ECL) emission efficiency, while the underlying ECL emission mechanism and the preparation of well-controlled morphologies with available functionalities have not been thoroughly investigated, significantly hindering their application in ECL sensors. In this study, we developed an effective method to prepare [Pt(bzimpy)Cl]+/TiO2 (PtII@TiO2) nanorods (NRs) (bzimpy = 2,6-bis(benzimidazol-2'-yl) pyridine) via a simple hydrolysis reaction of TiCl4 in the presence of [Pt(bzimpy)Cl]+. The hydrolytic process of TiCl4 could generate excessive H+, enabling the fast self-assembly of [Pt(bzimpy)Cl]+ complexes into well-controlled NRs, while the hydrolytic product TiO2 is prone to deposit on [Pt(bzimpy)Cl]+ surface to form PtII@TiO2 NRs. The ECL mechanism unravels that the self-assembled [Pt(bzimpy)Cl]+ NRs exhibited the aggregated-induced electrochemiluminescence (AIECL) effect. The catalytic capabilities of TiO2 and Pt (II) could accelerate the decomposition of co-reactant K2S2O8 to form SO4˙-, resulting in the significantly positive-shifted reduction potential and enhanced reduction current of K2S2O8, ultimately enabling the highly enhanced ECL emission of PtII@TiO2 NRs. Due to the high affinity of PtII@TiO2 towards the phosphate group via the formation of P-O-Ti coordination bonds, an ECL sensor for the profiling of protein kinase A (PKA) activity was developed with a broad linear range from 0.005 to 10 U/mL, and the limit of detection as low as 0.002 U/mL. This study provides a new strategy for the controlled self-assembly and functionality of square planar platinum (II) complexes with AIECL emission, which may extensively expand the potential applications of planar platinum (II) complexes in the ECL-based assays.