The　physicochemical　properties　and　application　performances　of　graphitic　carbon　nitride　(g-CN)　are　highly　dependent　on　its　polymerization　degree,　thus　a　facile　method　for　screening　the　polymerization　degree　is　highly　desired.　Here,　electrochemiluminescence　(ECL)　is　creatively　employed　as　an　effective　tool　to　achieve　this　goal.　Extension　of　π-system　and　change　in　pedant　groups　during　g-CN　polymerization　process　are　characterized　by　g-CN　nanosheets/dissolved　oxygen　(CNNS/O2)　and　Ru(bpy)32+/CNNS　co-reactant　ECL　systems,　respectively.　Linear　intensity　enhancement　along　with　positive　shift　in　the　onset　and　peak　potentials　of　cathodic　CNNS/O2　ECL,　as　well　as　linear　intensity　decreasing　in　anodic　Ru(bpy)32+/CNNS　ECL,　are　observed　during　polymerization　of　dicyandiamide　to　g-CN,　suggesting　the　feasibility　of　ECL　on　studying　the　polymerization　degree.　The　ECL　method　would　provide　a　promising　prospect　for　novel　properties　exploration　and　application　performances　optimization　of　g-CN.　©　2019　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim