It is significant for cell physiology to keep the homeostasis of pH, and it is highly demanded to develop ratiometric fluorescent sensors toward pH. In this work, under mild condition, through the electrostatic interaction between carbon nanodots (CDs) and organic molecules, two novel ratiometric fluorescence hybrid nanosensors were fabricated for sensing acidic pH. These nanohybrid systems possess dual emission peaks at 455 and 527 nm under a single excitation wavelength of 380 nm in acidic pH condition. With the increasing of pH, the fluorescence of the 1,8-naphthalimide derivative completely quenches, while the blue fluorescence of CDs keeps constant. Furthermore, the CDsorganic molecular nanohybrids exhibit excellent anti-disturbance ability, reversible pH sensing ability, and a linear response range in wide pH range respectively. Besides the ability to target lysosome, with one of the nanosensor, stimulated pH change has been successfully tracked in a ratiometric manner via fluorescence imaging.