The increased requirements on ranging precision in many military, industrial and astronomical applications illustrate the importance of the Laser ranging systems (called Laser radar) as a modern ranging system.  In this paper, the authors study the main features of laser ranging systems in its two main modes, the pulsed mode and the continuous wave subcarrier mode (CWSM).  The main advantages of each mode are discussed then proved out by experimental data given by the satellite ranging system Helwan and an experimental setup built on the bases of CWSM.  These results show good agreement with that expected theoretically.