Abstract: Some issues in the theory of soil arch in the geotechnical engineering are brought forward, including the forms of spandrel, the shape, geometric parameters and microscopic properties of soil archesetc. From the forming mechanism of soil arches, they are divided into four types,i. e.directly-forming spandrel, induced-friction spandrel, solum-forming spandrel and spandrel with different bases. Based on an engineering instance, some primary views on the geometric parameters of arch shape and arch body are put forward to develop and perfect the theory of soil arch.