Classic electrochemiluminescence (ECL) assays relying on the change in luminescence intensity face a challenge in the quantitative analysis of complex samples. Here, we report the design and implementation of a new sensing strategy, using the maximum luminescence wavelength (λmax) shift as the readout to achieve quantitative detection. This approach includes an ECL luminophore (RuSiO2@GO) and a H2S-sensitive inner filter absorber (CouMC). The absorbance of CouMC illustrates a dependence on the H2S concentration, which induces a change in the maximum luminescence wavelength (Δλmax) of the ECL luminophore. Both experimental and simulated results suggest that the spectral shift of ECL effectively avoids the interference of the total luminescence intensity fluctuations, enabling a highly reliable quantitative analysis. This spectral shift-based ECL assay strategy offers a wide application potential by extending types of ECL luminophores and absorptive chemodosimeters, based on an inner filter effect.