The separated heat pipe can effectively reduce the energy consumption of telecommunication base station, and the micro-channel heat exchangers can be adopted as the evaporator and condenser. In order to investigate the effect of the filling ratio on the heat transfer rate，EER，refrigerant pressure and temperature, and the variation of optimal filling ratio range and heat transfer rate under two air volumes and different outdoor temperatures, experimental test was carried out in the enthalpy difference laboratory, taken R22 as working fluids. The heat transfer rate and EER were 4.0 kW and 11.8, respectively, and the optimal filling ratio was 79.3% to 105.8%. The pressure of the system increased with the increase of the filling ratio. As filling ratio increased，the temperature difference between the inlet and outlet of the evaporator decreased firstly, and then increased slightly. When the air flow rate was reduced from 3 000 m3/h to 1 700 m3/h, the optimum filling ratio was almost remained, but the air temperature of evaporator outlet decreased and the maximum heat transfer rate decreased by 29%. Finally, the system was tested under different outdoor operating conditions. The test results showed that the range of the optimal filling ratio became narrow with the decrease of the outdoor temperature. The results are useful for modeling, design, and operation control of the micro-channel separate heat pipe.