The identification of pathogenic microorganisms is crucial to human health and industrial development, however, traditional culture-based methods are laborious and time consuming. We developed a novel method for the identification of pathogenic microorganisms based on single concentration-dependent carbon dots (CDs). The CDs were synthesized using a microwave heating approach without any complicated purification processes and the PL emission wavelength of the CDs could be tuned only by changing the concentration of the solution. The concentration-dependent CDs were applied for multicolor bioimaging and identification of eight kinds of microorganisms within minutes using different fluorescence spectra. This work provides a new approach for the detection of multiplex targets in real samples and lays a foundation for food safety monitoring.