Close cylindroid shells are widely used in many industrial branches. Membrane theory of shells is used to take an analytical solution to investigate the internal force distributions and deformation laws of such shells. The result shows that, under the condition of two-point simple supports, among three force components(meridional force T1, circumferential force T2, and shear force T12), T1 is the dominant one, which is negative (compressional) in the vicinity of the neutral axis, and becomes positive (tensional) after being away from the neutral axis. The shear force T12 is rather like a sine curve, which changes its sign at the neutral axis. This type of shear force distribution leads to a warp deformation within the cylinder. T2 is always the tensional force, and when comparing to the other two components, it is too small to be dominant in shell designing. Somewhat similar to the three force components, among the three deformation components, the normal displacement w is the extreme one, and also it varies acutely. The circumferential displacement v is much less than w, which is compressive below the neutral axis, and becomes tensile above the neutral axis. In the nearby of neutral axis, v is nearly zero. Compared to w and v, the meridional displacement u is always the minimal.