The advent of femtosecond optical frequency comb (FOFC) offers many available solutions for absolute distance measurement,as is expected to be directly applied to many space ranging tasks,such as laser radar,satellite formation flying and gravity field measurement.With a purpose of precision requirement for future space ranging,an integrated method based on time of flight method and optical pulse cross-correlation analysis is proposed,making the distance traceable to the repetition rate of frequency comb.The fundamental model for laser ranging with FOFC is built,theoretical analysis for femtosecond pulse cross-correlation is implemented,and simulations for cross-correlation and large-scale ranging are demonstrated.The simulation result shows that when the target distance is near 10 km and the scanning precision for repetition rate is 0.01 Hz,the measurement accuracy is better than 450 nm within the linear test of a non-ambiguity range,and the peak-valley (PV) value of residual errors is less than 780 nm,validating that the proposed scheme is feasible for large-scale space ranging with submicron precision or even nanometer precision.