The invention belongs to the technical field of projectile body high-speed penetration tests, and provides a projectile blocking support device for a long-rod projectile subcaliber high-speed launching test. The provided projectile blocking support device for the long-rod projectile subcaliber high-speed launching test is provided with a supporting plate I (4) welded to a target bearing frame; a supporting plate II (1) concentric with the supporting plate I (4) is placed on the supporting plate I (4); the supporting plate II (1) is a round plate with a through hole in the center; a buffer plate (2) is placed on the supporting plate II (1); an energy consumption plate (3) is arranged on the buffer plate (2); the buffer plate (2) and the energy consumption plate (3) are both a square with a round through hole in the center and are both fixed to the supporting plate II (1). The influence of projectile support collisions on projectile body flying postures is reduced; the requirement that a projectile body keeps the original trajectory posture in the long-rod projectile subcaliber high-speed launching test is guaranteed.