The invention discloses a method for manufacturing stretch wool yarns, which comprises the following steps: 1) adding a hygroscopic agent and a reducing agent in wool fabrics; 2) drying the wool fabrics; 3) spinning; 4) performing a moist-heat treatment; 5) untwisting the yarns; and 6) detwisting the yarns. After the addition of the hygroscopic agent and the reducing agent, the wool fabrics are spun and twisted into yarns, and then subjected to the moist-heat treatment so as to effectively shape the twisted yarns; and the yarns are twisted further in a reversed direction of the original twisting direction to form a spiral shape so as to achieve excellent flexibility; therefore, the stretch wool yarns applied to various materials for clothing or other purposes can be obtained easily; the stretch wool yarns have a flexibility rate of 250 percent and also have the characteristics of bulked yarns.