Measurement of the integrated luminosity at root s=3.650, 3.686 GeV for the BES detector

The integrated luminosity for the two sets of BES data, collected at roots = 3.650, 3.686GeV in 2002 and 2003, are carefully studied, and measured to be (6.42 +/- 0.24) pb(-1) and (19. 72 +/- 0. 86) pb(-1). The result provides basic input parameter in the measurements of cross sections at the above two energy points.