Urinary light chains are small molecules of immunoglobulins that can be reabsorbed by the renal tubules through the glomerular basement membrane and returned to the body’s blood circulation. If a large amount of urinary light chain is excreted in the body’s urine, it indicates that the renal tubules may be severely damaged, and the normal body will not detect urinary light chain in urine examination. Since urinary light chain is secreted by plasma cells, if the value is too high, it is usually caused by systemic diseases such as myeloma causing monoclonal plasma cell hyperplasia, Walden’s macroglobulinemia and light chain amyloidosis, etc. Further tests are needed to clarify the diagnosis. Since urinary light chain has an important clinical significance, once the problem occurs, it should be treated promptly by a doctor. Currently, for the treatment of urinary light chain disease, commonly used drugs include thalidomide, bortezomib and lenalidomide.