Abstract: In order to improve the capacity of performance of large scale terrain data, users usually create detail data by editing way such as changing the features in some regions and add other details to original terrain data in some simulation training or video games. However, its a big challenge to merge and render large terrain and additional detail data in real time due to different resolutions. In this paper, a new algorithm is given to handle this problem. In preprocessing stage, the algorithm constructs large terrain by clipmap structure as to integrating advantages of geometry clipmap method and constructs the detail data in mipmap way. In real-time rendering phase, the phenomenon of “F” hole area appears at the boundary between the large terrain and the detail data when clipmap structure is being updated. In order to solve this problem, a new structure called transition strip is proposed which can merge the data in different resolutions well in run time, the transition strip structure is given which is composed of two sides, the vertexes in lower resolution and vertexes in higher resolution. Some transition strips are used to fill the “F” hole area and these transition strips are close to each other in practice. And a fast triangulation method used for rendering. The results of experiments show that the transition strip can solve the problem of “F” hole area and can render both large terrain and details data in real time.