Abstract: Gold nanoparticles were prepared via a simple photoreduction technique in the presence of Keggin heteropolyacid doped with different transition metals (PW₁₁M),in which the Keggin heteropolyacid acted as reducing agent,photocatalyst and stabilizer.The results indicate that formation rate and morphology of the particles strongly depend on the kind of transition metal doped in the heteropolyacid and the preparing conditions such as irradiation time and propan-2-ol amount.The photoreduction rates of PW₁₁Zn and PW₁₁Fe are faster than those of PW₁₁Ni and PW₁₁Cu.The shapes of the nanoparticles synthesized in the presence of PW₁₁Fe and PW₁₁Zn are nearly uniform spheres,while the morphologies of the nanoparticles synthesized in the presence of PW₁₁Ni and PW₁₁Cu are found to contain a mixture of flat triangular/hexagonal structures as well as spheres.The increases of irradiation time and propan-2-ol amount can make the morphology of the nanoparticles more uniform and shorten the formation time of the nanoparticles.