  The development of the GPS (Global Positioning System) signal simulator
involving to a number of key technologies, in which the generation of
navigation message has important significance. Based on analysis of the
structure of GPS navigation data, the paper researches the production of
telemetry word and handover word, parity check code, time parameters and star
clock. Using disturbing force equation and Lagrange planetary motion equation
extrapolate ephemeris parameters whose feasibility is verified through the
Matlab software finally.
