The Beijing Electron Positron Collider (BEPC) is a two-ring e⁺e^– collider running in the tau-charm energy region (Ecm=2.0-4.2 GeV), which, with a design luminosity of 1×10³³cm^-2s^-1 at the beam energy of 1.89 GeV, is an improvement of a factor of 100 over its successful predecessor, BEPC. BEPC II consists of the injector, the storage ring, the transportation line, the Beijing Spectrometer (BES), the Beijing Synchrotron Radiation Facility (BSRF) and the computer center.

The collider consists of two 237.5 m long storage rings, one for electrons and one for positrons. They collide at the interaction point with a horizontal crossing angle of 11 mrad and a bunch spacing of 8 ns. Each ring holds 93 bunches with a beam current of 910 mA.