The invention relates to a preparing method and application of an electrochemical luminescence sensor based on a silver oxalate bridging tris (bipyridine) ruthenium nanometer composite, and belongs tothe field of nanometer materials and analysis chemistry. A metal functionalization graphene oxide-silver oxalate/ tris (bipyridine) ruthenium nanometer composite material and a ferroferric oxide poly-dopamine core-shell composite material are utilized to prepare the electrochemical luminescence sensor, and the electrochemical luminescence sensor is used for sensitity detection of N-terminal pro-B-type natriuretic peptide.