Hexagonal boron nitride/gold nanocomposites (h-BN/Au NCs) were fabricated and developed for ultra-sensitive detection of crystal violet (CV) and creatinine molecules using surface enhanced Raman scattering spectroscopy (SERS). The overgrowth of Au nanoparticles was driven by laser-induced photoexcitation of h-BN, which was monitored by absorption spectra. The h-BN/Au NCs with controllable Au compositions (0-1.85%) were characterized using Transmission Electron Microscopy (TEM), Scan Electron Microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). The microstructural analyses indicated that mono-dispersed Au nanoparticles with size of similar to 10 nm can be accreted on h-BN via 30 min synthetic reaction. The comparative SERS results reveal that the h-BN/Au NCs with 1.68% Au composition provide enhanced SERS activity in comparison with other nanosubstrates in this paper. The corresponding enhancement mechanism of h-BN/Au NCs has been illustrated in detail, which can be composed of four contributions in our research. Then, the SERS analyses demonstrated that the detection limit of CV molecules was achieved at femtomole level of similar to 10(-15 )M, leading to ultrasensitive monitoring of dye pollution. More importantly, well-defined linear relationships were established between SERS signal intensities and logarithmical scale of creatinine concentration (10(-2)-10(-6)M), providing a precise assessment of creatinine in pathological diagnostics.