The desirable self-enhanced ECL luminophore was achieved by combining the coreactant of L-arginine(L-Arg) and the luminophor of tris(4,40-dicarboxylicacid-2,20-bipyridyl) ruthenium(Ⅱ) dichloride(Ru(dcbpy)2+3) to form a novel Ru(Ⅱ) complex,combing with an excellent conductivity property and large surface areas of the Au nanocages(AuNCs),an alternative for ultrasensitive detection of α fetoprotein(AFP) was designed utilizing the self enhanced electrochemiluminescence(ECL) of a novel Ru(Ⅱ) complex.For this proposed immunosensor,thiolated carbon nanotubes which were dispersed in Nafion solution were modified on the bare glass carbon electrode.Subsequently,hollow gold nanospheres(HGNPs) were assembled onto the modified electrode by Au-S bond,which could further improve the ECL intensity and be favorable for the adsorption of antibody.The measurement was based on a sandwich immunoassay method.The experimental results demonstrated that the proposed immunosensor exhibited a sensitive and stable response for the detection of AFP.The calibration curve was linear in the range of 1.0×10-5-1.0×10-3 ng/mL,with a limit of detection(S/N=3) of 3.3 fg/mL.