Following the approval of the Chinese government, the major upgrade of the Beijing Electron Positron Collider (known as BEPC II), the largest scientific facility proposed in our country is carried out in an all round way.

　　As one of the eight major centers for high energy physics in the world, the Beijing Electron Positron Collider National Laboratory leads the world in the study of charm physics. Its attainment of the results has turned the experimental study of charm physics into an issue of general interest and one of the frontiers of high precision measurement during the intense competitive study of high energy physics in the world. Precision measurements require that high performance accelerators provide even more data and that high performance detectors be used. Therefore the current BEPC has to be thoroughly upgraded with the luminosity greatly improved so that it can become a double ring collider.

　　The total budget of BEPC II is estimated at 640 million Chinese yuan (77 million US dollars), The construction period is 5 years. During the major upgrade, the most advanced double ring angle colliding technology will be used, that is to say, one more storage ring will be added in the existing BEPC storage ring so that the electrons and positrons can travel separately in their own storage ring. The number of e+ e- colliding bunches will be increased to 93 from 1 in each ring. Together with other technologies adopted, the performance of BEPC II will be increased by a factor of 100. Its design luminosity is 1033 cm-2s-1 at the center-of-mass energy 3.77 GeV. At the same time, the Beijing Spectrometer (BES) will also be thoroughly upgraded in order to improve its measurement precision, reduce the system error and cater to the requirement of high counting rate in operation after the upgrade.

　　The upgraded BEPC will maintain its leading position among accelerators of the same kind in the world and become one of the most advanced double ring colliders in the world for precision measurement in the τ charm energy region and probing new physics. It is expected that several important world-class results will be achieved in the study of the frontier τ charm physics, such as search for gluball, quark-gluon hybrid and exotic particles, precision measurement of CKM matrix element, study of charmonium spectra and its decay property, study of light hadron spectra and baryon excitation, precision measurement of R value of hadron in the 2-5 GeV, study of D physics, etc. and probing of new physics.

　　During the upgrade, a lot of the most up-to-date high technologies will be adopted, involving RF superconductivity, high power microwave, high precision magnetic field, stable current and pulsed power supply, ultra vacuum, high voltage, precision machining, computer automatic control, high performance superconducting magnet, sophisticated detector, new type of fast electronics, parallel processing using PC farm, storage area network, large database, etc. The introduction, development and popularization of these technologies will greatly improve the level of related industries in China. The domestic and international collaborations carried out in the above-mentioned fields will turn the BEPC into a window and platform for the cooperation and exchange of high technologies.