Gold nanoparticles were prepared in surfactant solutions by reduction of HAuCl4 under UV irradiation without adding extra reductants or other organic substances. The effect of the structure and the property of surfactant on the size and the optical properties of prepared gold nanoparticles were studied. It was found that the longer the alkyl chain of the surfactant, the larger gold particles are obtained. On the other hand, lengthen the geminis spacer benefits the formation of smaller gold particles. The formation of adduct micelles composed of the charged surface active portion of the surfactant molecule and the (AuIIICl4)− ion in cationic surfactant solution serves as the gold source and favors the formation of gold particles with larger sizes. While the repulsion between the (AuIIICl4)− ion and the negative charged surface of anionic surfactant micelle is in favor of the formation of gold nanoparticles with smaller sizes. The nonionic surfactants can also assist the formation of dispersed gold nanoparticles.Highlights► The properties of surfactants determine the sizes of synthesized god nanoparticles. ► The surfactant act as soft template, controller of gold source as well as stabilizer. ► The adduct micelles favor the formation of gold nanoparticles with bigger sizes. ► The anionic surfactants can assist the formation of smaller gold nanoparticles.