Abstract: Sliding interface status during whole electromagnetic rail launch process depends on contact status after initial assembly in which initial contact force between armature and rails(A-R) is provided by trailing arm elastic deformation in the C-armature rail launcher, which influences launcher system efficiency and rail lifespan. This paper focuses on the contact status of initial C-armature assembly of rail launcher with constructing the contact model for simulating computation and designing many groups of experiments for contrast testing. Considering safe deformable limits of armature material, variation laws of contact pressure, contact region(area) and contact force are analyzed under conditions of small-range feasible heads and tail sizes. Interferential proportion is proposed as a contact status dependent key parameter. Contact region transformed from tail to head of trailing arm as interferential proportion increasing, maximum of contact area is about half of whole outer surface of trailing arm. Optimal contact status for favorable electric contact and engineering implement technique are also discussed.