Abstract: The lateral displacement of composite soil nailing is a key parameter for design, but the calculation method is not specified in the code. This paper adopts the assumption that the final lateral displacement of the composite soil nailing wall is the sum of the micro-pile deformation under partial soil pressure and the pull-out deformation of soil nail in its effective range, and the former is equivalent to that of a multi-span beam under partial soil pressure. Then the calculation model of the lateral soil pressure applied to the micro-pile is proposed by the magnitudes of the horizontal stiffness of the soil nail and the micro-pile. The formula of horizontal stiffness coefficient of soil nailing is derived, which is mainly affected by the shear deformation coefficient among the nailing soil at the corresponding position and the soil nail length (L1) outside the potential sliding surface. The horizontal stiffness coefficient of the micro-pile is calculated as per the cantilever beam or lateral load bearing pile. Some parameters presented in practical calculation method of soil nailing displacement are discussed including soil pressure style, shear displacement coefficient and calculation method of overall stability. One engineering example is used to demonstrate the validity of the proposed method .With the result derived from pullout tests, the practical calculation method can serve as a theoretical basis in the predictive control of soil nailing displacement.