Briefly saying, Egyptian Pyramid of Khufu is supposed to be as a kind of huge sand pile, which includes religious structures inside and has stone walls outside. It might be considered that the lower parts of main inner religious structures and the outside stone blocks obliquely heaped were built at first and then sand filed up in the space between them. Then, repeated the same process, the pyramid could be completed. The sloped masonry works as retaining walls and gives them a good appearance. The slope angle of the surface of pyramid may have some relationship with the angle of repose of sand. The so called inversed staircase of the great corridor in the pyramid is only stone boards of the ceiling. Therefore, the construction of the Egyptian pyramids might be not so extremely difficult works.