The recent development status, scientific missions, system configuration, progresses and future development trend of international GNSS occultation projects, including GPS/MET, Orsted, Sunsat, SACC,CHAMP, GRACE, FedSat, COSMIC, METOP and ACE+ projects, are introduced in detail. It is pointed out that occultation sounding technology has made great progress in operational application since the implementation of GPS/MET project. The development of GNSS occultation sounding will turn to the multistar integration, and the international cooperation in the development among projects will become a trend in the future.