GNSS(Global Navigation Satellite System) precision orbits and clocks product is the premise of realizing high-precision PPP(Precise Point Position) and the basis of high-precision GNSS application. Therefore, it is of great research significance and application value to develop a combination method of GNSS orbits and clocks product and realize a stable and reliable orbit and clock combined product service. This paper introduces the general situation of the GNSS constellation and IGS(International GNSS Service) service center, combs the functional model of orbit clock combination synthesis, comprehensively analyzes and discusses the progress of GNSS orbit clock combination product synthesis technology, and looks forward to the opportunities brought by existing research on GNSS real-time orbit clock combination synthesis and real-time precise single point positioning.