A new organic-soluble co-reactant of N,N,N’,N’-tetrakis(propyl)-pentanediamine (TPPD) was synthesized and co-immobilized with tris ( 2, 2’-bipyridine ) ruthenium ditetrakis ( 4-chlorophenyl ) borate ([Ru(bpy)3][4-(Clph)4B]2) on an indium tin oxide (ITO) electrode for electrochemiluminescent (ECL) study. The hydrophobicity of TPPD prevented its leakage from the electrode surface, thus the long-term stability of the ECL electrode was enhanced. The TPPD/[Ru(bpy)3][4-(Clph)4B]2 modified-ITO electrode exhibited strong, stable and reproducible ECL signal. The ECL signal could be quenched efficiently by phenol with a quenching efficiency of 95. 4% in the presence of 0. 1 mmol/L phenol, demonstrating the potential of the modified electrode in determination of phenolic compounds. The transient-state of the electrogenerated chemiluminescence reaction was also investigated, which revealed that the TPPD/[Ru(bpy)3][4-(Clph)4B]2 modified-ITO electrode had a longer lifetime than conventional TPA-Ru(bpy)2+3 co-reactant system.