The method of using microwave phase to measure short displacement was presented in this paper. A resonance cavity structural microwave sensor model based on this principle was established and simulated. The ability for measure blade tip clearance on aircraft engines and the effect of high temperature for the sensor were analyzed. The result shows a high accuracy measure ability of the sensor in 0-6mm clearance under high temperature environment, and verifies a good application in blade tip clearance measurement on aircraft engines.