he steel lined reinforced concrete penstocks (SLRCP) is always looked as an axisymmetric structure according to the design code, which can not show the true load-carrying capacity when considering the dam’s constraint to the SLRCP. In this paper, the physical non-axisymmetric property of the structure is simulated using the finite element method. The internal force distribution of every cross section in the SLRCP is studied, and a design method for steel arrangement based on axial force is proposed. When considering the non-axisymmetric property, the axial force in those cross sections approaching the bottom of the structure may be reduced more than 30% to the calculated value by the axisymmetric analysis. The larger the inner radius of the penstock or the thickness of the concrete wall is, the more marked the non-axisymmetric property of the SLRCP is.