Abstract: The longitudes determined by dynamical satellite geodesy using Doppler and(or) laser data are relative to an assumed origin.In order to obtain the"absolute longitudes",it is necessary to determine the longitude orientation of Doppler(laser) network in the CIO-BIH system.In this paper the reason caused the longitude orientation in the Doppler(laser) network is discussed;the fomulae determining the longitude orientation using the simultaneous photography are given;the optional observation conditions are discussed in detail and the accuracy of this method is estimated.