Regulating the dimethyl methanephosphonate (DMMP) adsorption capacity of graphene-based sensing materials is crucial for their promoting practical applications for DMMP detection at room temperature; however, this still remains challenging. Herein, because carbon nanodots (CDs) possess the major active sites in newly developed reduced graphene oxide (rGO)-based sensitive materials (Cu 2 + and CDs co-modified rGO), an enhancing DMMP adsorption capacity strategy via hydrogen bond and Fermi level dual modulating engineering was proposed to improve DMMP sensing performances. Experimentally, four kinds of CDs with various fluorescent properties (blue, yellow, orange, red) were prepared and their affecting on the adsorption of DMMP was investigated. Interestingly, the red emission CDs (RCDs) and Cu 2+ co-decorated rGO (rGO-RCDs-Cu) exhibits a high response value of 24.05% toward 340 ppb DMMP, low limit of detection of 17 ppb, high selectivity and high stability, overwhelmingly superior to previous rGO-based DMMP sensors. Depended on the hydrogen bonding interactions between DMMP and CDs, supported by the change of N-H peak in 1H nuclear magnetic resonance ( 1H-NMR) spectra and the observation of the signals for P=O bonds in Raman and Fourier-transform infrared (FT-IR) spectra after adsorption of DMMP. The improvement of DMMP sensing performances for rGO-RCDs-Cu is attributed to the enhanced DMMP adsorption capacity of RCDs (especially compared to BCDs), which was supported by high quenching efficiency and large equilibrium constant for adsorption of DMMP by RCDs in the fluorescent spectroscopy-assisted analysis strategy. This study provides new insights into fabrication of high-performance carbon-based room-temperature gas sensors by modulation of gas adsorption capacity engineering.