China aviation project has little sample and the traditional method can not estimate the project cost accurately. This paper proposes a method estimating aviation project cost based on gray systematic theory. We divide aviation product into systems or parts and regard them as cost estimation unit. The gray forecasting model GM (1, 1) was set up based on historical cost data of cost estimation unit. If the model’s precision doesn’t meet with the requirement of aviation project cost estimation, the revision model GM (1, 1) must be set up to raise the estimation precision The experimental results show the method can get the more high-accuracy estimation value using the little sample and is suitable for the cost estimation of the our country aviation project.