To sensitively detect cardiac troponin I (cTnI), a novel electrochemiluminescence (ECL) immunosensor was constructed on the basis of the core-shell MoC combined with carbon material (MoC@C) nanosphere as an ECL super-enhancer and a label of secondary antibody (Ab). MoC@C nanosphere with excellent conductivity and high chemical stability could increase the ECL intensity of the tris-(2,2'-bipyridine)ruthenium (Ru(bpy)). MoC@C/polyethylenimine (MoC@C/PEI) firmly anchored Ab by covalent bonding. Otherwise, amino-modified multiwall carbon nanotubes@nafion (MWCNTs-NH@N) composite film, as substrate material, could connect with the Ru(bpy) by ion exchange and immobilize primary antibodies (Ab) by amide bond. In addition, the boron nitride quantum dots (BNQDs) were utilized as the co-reactant, which were synthesized by using low-cost material melamine as a nitrogen source. Under optimal experimental conditions, the proposed ECL immunosensor possessed a low detection limit of 0.03 pg/mL (S/N = 3) and a wide linear range from 0.1 pg/mL to 50 ng/mL. The ultrasensitive ECL immunosensor had excellent stability, outstanding specificity and great reproducibility. It was also used to detect cTnI in human serum with satisfactory results.