With the development of science and technology, digital city attracts more and more attention and the need for 3D models of urban buildings is increasing. Many researchers have proposed different ways for 3d building model reconstruction, among which some are semi-automatic; some are automatic but very complex. This paper presents a novel method for reconstruction of 3D building models from aerial images and Light Detection Ranging (LiDAR) Data. The proposed method is automatic, fast, simple and convenient. First an image is generated from airborne LiDAR data. Gray levels of pixels in the image are obtained from height information of the points in LiDAR Data. The image is then processed and buildings are extracted from it. Textures of the buildings and the ground are obtained from aerial images. At last buildings are reconstructed with the information of coordinates, height and textures. Experiments show that this method is very fast and effective.