Surface-enhanced Raman spectroscopy (SERS) is a fingerprint technique with ultra-high surface sensitivity down to single-molecule level. It can be used for specific, fast and nondestructive detection of trace amounts of molecules, which has been widely applied in various fields, such as life sciences, electrochemistry, environmental safety and even our daily life. Herein, highly uniform Au nanoparticles with tunable sizes are prepared via a seed growth method. They have been used as SERS substrates for detection of uric acid. Size dependent SERS enhancements have been found for the Au nanoparticles, and the enhancements increase with the particle size. Au nanoparticles with size of 150 nm are the optimized substrate for the detection of uric acid, when the laser with wavelength of 638 nm is used as exciting light. The detection limit of uric acid is 001 mmol·L-1. It has also been found that Au nanoparticles could be used for the quantitative detection of uric acid. The result shows that there is a linear relationship between the Raman intensity of the peak at 640 cm-1 and the concentrations of uric acid in the range of 001～05 mmol·L-1. Therefore, this method can be used for rapid detection of real samples (normal human urine). It is not affected by the interference of other components in urine, thus, it can realize the rapid determination of uric acid in human urine. This work greatly expands the clinical application of surface enhanced Raman spectroscopy.