The 13 nm gold nanoparticles were synthesized and were modified with Bisphenol A(BPA) aptamer. The oil-solubility Up-conversion nanoparticles (UCNPs) were modified with polyacrylic acid (PAA) to form water-solubility UCNPs. Then water-solubility UCNPs were coated with the complementary DNA strand. Based these nanoparticles, a FRET aptasensor for BPA was successfully fabricated by using Up-conversion nanoparticles as energy donor and gold nanoparticles as energy acceptor. The results show that the detection system has a good linear relationship at 1×10^-9～1×10^-3 mol/L (R²=0.992 3), and the detection limit is as low as 1×10^-10 mol/L. The method is proved to be of good practicability through the experiment of adding the standard of water and milk samples.