Controlled radical photopolymerization of n-butyl methacrylate(n-BMA) mediated by 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy(HTEMPO) was carried out in bulk at ambient temperature. It was found that obtained n-BMA homopolymers exhibited narrow polydispersities of around 1.4, which was characterized by GPC. Plots of number-average molecular weight vs. conversion and Ln([M0]/[M]) vs. time were liner respectively, indicating that was a controlled photopolymerization.