The invention discloses a low-strength-loss shrink-proof finishing method for a wool fabric and belongs to the technical field of wool fabric dyeing and finishing processing. According to the method,firstly, DCCA is adopted for conducting chlorination shrink-proof treatment on the wool fabric, then the wool fabric is soaked in a chitosan finishing solution and a cellulose nanocrystal solution insequence, assembly is conducted 10-20 times, the anti-felting performance of the treated wool fabric is obviously improved, in addition, the strength loss of the fabric is also greatly lowered, and the hand feeling of the wool fabric is good.