Improved measurement of the branching ratio of J/psi-->K_S K_L

The branching ratio of J/psi-->K_S K_L is measured with improved precision to be B(J/psi-->K_S K_L) = (1.82\pm 0.04\pm 0.13)\times 10^{-4}. using J/psi data collected with the Beijing Spectrometer (BESII) at the Beijing Electron-Positron Collider. This result is used to test the perturbative QCD ``12%'' rule between psi(2S) and J/psi decays and to investigate the relative phase between the three-gluon and one-photon annihilation amplitudes in J/psi decays.