This research is about applying SCINS (Simply Constructed Inertial Navigation System) in vehicle trajectory prediction, base on INS (Inertial Navigation System), combine with vehicle dynamic to know the vehicle’s trajectory and posture, use MATLAB to simulate and prove the theory, build up a SCINS and numbers of track to test the accuracy, only needs a gyro and two accelerometers, present a coordinate transform by Eular transform that can use in SCINS, and present a method that can predict vehicle’s trajectory by using the information from SCINS, and proved it by experimentation .