Gold nanoparticles (AuNPs) were synthesized by ethanol in a base environment. Electron microscopic images characterized the sizes of AuNPs. UV-Vis spectrometer was utilized to study the absorption spectra of gold colloid and the effect of different factors for synthesis. It is found that the quantity of sodium hydroxide (NaOH) is an important factor in determining the formation of the final colloidal product. X-ray diffraction (XRD) analysis was conducted to examine the crystalline structure of the AuNPs, and indicating the nanoparticles present a face-centered-cubic (fcc) crystalline structure. Moreover, the possible mechanism of the progress and the effect of NaOH on the reduction reaction were discussed. The alcohol and hydroxyl ions (OH-) are indispensable to generate the gold particles for one-step at room temperature in just few minutes