Abstract: An isolator with a full ramp was designed to improve the performance of the isolator or to reduce the length of the isolator.The ramp was placed on the lower wall at the isolator entrance.Experiment was conducted in Mach 1.98 at the isolator entrance.Experimental results indicate that,the length of the shock train is reduced by 19.8 percent for the rectangular isolator with the full ramp.The length of shock train in the isolator without a ramp is 13.87 times the height of the isolator entrance,but the length of shock train in the isolator with the full ramp is reduced to 11.12 times the height of the isolator entrance under the same back-pressure cases.The maximum back-pressure is improved by 8.45 percent for the isolator with a ramp which can withstand a maximum back-pressure of 3.85 times static pressure,but the isolator without a ramp could only withstand a maximum back-pressure of 3.55 times static pressure.