Abstract: Aiming at the fact that many researchers did not understand the concept of GPS/SINS time synchronization clearly,understanding of time synchronization was proposed.Firstly,time delay of serial navigation data relative to 1 pps of Novatel GPS receiver was measured by an oscillograph,based on which time synchronization error of GPS/SINS integrated system including this GPS receiver was estimated,which was between 0.6 s and 1.6 s.Then,a vehicle experiment was accomplished with an integrated system comprised of this receiver and a military airborne SINS.Experiment results showed that time synchronization error fitted with vehicle experiment data was about 1.1 s,which illustrated that the description on the concept of GPS/SINS integrated system time synchronization in this paper is practical.