Energy transfer between chemiluminescence (CL) donor and acceptor enables the tunable long-wavelength emission for multidisciplinary applications. In this work, the carbon nanodots (CDs) with sp³-hybrid carbon nitride framework exhibit a conspicuous tunable CL wavelength in luminol–H₂O₂ reaction with ultrahigh energy transfer efficiency. The density functional theorical calculations and experimental surveys reveal that the synergistic effect of singlet/triplet mixed electron exchange between the CD and luminol–H₂O₂ reaction enable the efficient energy transfer, and the concentration-dependent distance between the luminol donor and CD acceptor mutate the efficiency of singlet/triplet electron exchange, leading to the efficient concentration-dependent CL emission. With the novel CL emission, an advanced paper-based CL system is established with the CDs and luminol–H₂O₂ reaction, and the applications of information encryption and anti-counterfeiting are achieved. This work paves a new paradigm to understand the energy transfer mechanism in CL process, and may inspire the design of new CL architecture.