Simple and efficient strategy to obtain ideal organic electrochemiluminescence (ECL) luminophores still is a central challenge. Here a series of coumarin microcrystals (C545 MCs) as new generation of ECL luminophores were facilely synthesized by a solvent exchange process. Among them, leaf-like C545 MCs with donor-acceptor system display a stable and robust anodic ECL response with triethanolamine (TEOA) as coreactant, which is 9.28 times higher than that of C545 monomer. Combined with its predecessors (coumarin and coumarin 6 H), the effects of donor and acceptor on the ECL properties of C545 were investigated with the help of experiments and theoretical calculation. On the basis of the quenching effect of dopamine (DA) toward the C545 MCs-TEOA ECL system, it was employed to construct a sensitive sensing platform for DA detection. A low limit of detection (0.38 nmol·L−1, S/N = 3) is obtained in a wide linear range (1 nmol·L−1 – 1 mmol·L−1). This work forcefully enriches the design and application of donor-acceptor based coumarin materials in ECL sensing.