The invention relates to a spiral spring without a parallel ring. A wire rod is coiled to be in a spiral shape; the spring is in symmetrical structure via the way of taking middle ring of the spring as a center; the intermediate diameter of the spiral spring is gradually reduced from the middle ring to the two ends of the spring; the outer diameter of a next ring is less than the inner diameter of a last ring; and the less quantity is more than the maximum manufacturing tolerance total of adjacent two rings.