Ultrathin (UT) g-C3N4 with a thickness of similar to 2 nm was prepared via a facile thermal exfoliation method using bulk g-C3N4 as precursor. The UT-g-C3N4 sample obtained exhibited a large specific surface area of 192.9 m(2).g(-1). The UT-g-C3N4/Ag hybrids were fabricated by a photo-assisted reduction technique. The morphology, microstructure and composition of the UT-g-C3N4/Ag hybrids were systematically characterized by transmission electron microscopy (TEM), aberration-corrected scanning transmission electron microscopy (STEM), STEM-energy dispersive X-ray (EDX) spectrometry, atomic force microscopy (AFM), X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). Based on electrochemical impedance spectroscopy (EIS) results, the optimal UT-g-C3N4/Ag hybrids displayed a faster electron transfer rate in comparison of UT-g-C3N4 and bulk g-C3N4. Moreover, in the presence of a phosphate buffer solution (pH = 6.0), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) results showed that the UT-g-C3N4/Ag hybrids coated on glassy carbon electrode (denoted as UT-g-C3N4/Ag/GCE) exhibited excellent electrochemical properties for L-tyrosine detection. It is observed that the electrochemical response of was linear in the concentration range of 1.00 x 10(-6) to 1.50 x 10(-4) mol L-1 with a limit of detection (S/N = 3) of 1.40 x 10(-7) mol L-1, superior to the other reported sensors. The developed UT-g-C3N4/Ag/GCE sensor was employed for L-tyrosine detection in commercial L-tyrosine tablet samples, and the recovery of 97.2-99.3% was observed. This proposed g-C3N4-based electrochemical sensor provides a rapid and sensitive sensing method for L-tyrosine detection in real samples.