The cosine-distributed impulsive loads induced by intense soft X-ray radiation are often simulated by explosive rods in laboratory tests. The conventional design method of rods distribution needs a complicated process, by trials or optimization, to ensure the rod number as an integer. This paper proposes a simplified method based on the principle of load discretization and impulse equivalence. It has higher efficiency and more convenience, and can automatically let the rod number be an integer. This study provides an effective design tool for rod-explosive simulation tests of aerospace structures under intense soft X-ray radiation.