The requirement to non-invasively quantify H + is gradually increasing. In this regards, optical pH sensors based on fluorescent materials have advantages. However, the stability and sensitivity of currently used chromophores still need to be further improved to meet the continuous increase in actual demand for pH measurement. Here, we proposed to employ Montmorillonite (MMT) nanosheets as matrix and carbon dots (CD) as chromophores to fabricate a new complex. The as-prepared MMT-CD have the following advantages: 1) the aggregation of CD is effectively reduced, leading to the effectively improved fluorescence performance; 2) MMT-CD has good light stability and storage stability; 3) as-prepared the fluorescence pH sensor shows good response to pH, high sensitivity, and wide linear range. Therefore, MMT-CD materials have great potential in the rapid and sensitive sensing of pH value.