Gold nanoparticles were prepared via a simple photoreduction technique in the presence of transition metal monosubstituted Keggin heteropolyanions (PW11M, M= Cu2+, Ni2+, Zn2+, Fe3+), in which PWllM acted as reducing agent, photocatalyst and stabilizer. The results indicated that the formation rate and morphology of the nanoparticles strongly depended on the kind of transition metal substituted in heteropolyacid and the preparation conditions, such as irradiation time and propan-2-ol amount. The photoreduction rates of PWllZn and PWllFe were faster than those of PWllNi and PW 11 Cu. The shapes of the nanoparticles synthesized in the presence of PWllFe and PWllZn were nearlyuniform spheres, whereas the morphologies of the nanoparticles synthesized in the presence of PW11Ni and PW11Cu were found to contain a mixture of flat triangular/ hexagonal structures as well as spheres. Increases in the irradiation time and the propan-2-ol amount could make the morphology of nanoparticles uniform and shorten the formation time of the nanoparticles.