Aircraft vibration has an effect on airborne gravity and gravity gradient measuring system.In order to have a full understanding of aircraft vibrational characteristics and provide some advices and references for instrument system ranges and physical design,the authors carried out a large amount of measurement and depth analysis of vibration characteristics of Y-12 and Cessna 208 aircraft.The results show that the vibration of aircraft floor is mainly caused by the engine,the propellers speed shows regular multiple frequency distribution in vibration energy,and its fundamental frequency of multiple frequency is expressed as fundamental frequency of propellers speed multiplied by the propeller vane.The vibration of the aircraft under flight conditions is the typical periodic vibration signal.