A series of approaches have been developed to identify the short take-off performance of tilt-rotor aircrafts which tilt their nacelles to implement short take-off. The approaches include how to confirm the minimum tilt angle of the nacelles, and the formulas suitable to calculate lift-off speed and take-off length are also developed. These methods are adopted in the design of a certain tilt-rotor aircraft during the preliminary design stage, moreover, the effects of airport altitude and weather conditions on short take-off performance are also researched. The results are reasonable, which indicates that these approaches are useful and of great value in practice.