Abstract: Objective To explore the diagnostic value of immunofixation electrophoresis and Kappa/Lambda (KAP/LAM) ratio in multiple myeloma patients with renal injury. Methods The serum of 822 patients of renal disease were collected for the examnation of immunofixation electrophoresis, KAP/LAM ratio, serum immunoglobulin levels and renal function，including serum urea nitrogen (BUN), serum creatinine (Crea), cystatin C (Cys-C) and estimated glomerular filtration rate (eGFR). To analyze the diagnostic value of immunofixation and KAP/LAM ratio in the differentiation of renal injury of multiple myeloma from primary renal injury diseases. Results M protein was observed in 75 patients (9.1%). The ratio of each type was IgG 49.3%(37/75), IgA 34.7%(26/75)，IgM 5.3%(4/75) and LAM 10.7%（8/75）. There was significant difference of KAP/LAM ratio between M protein group and non-M protein group. The KAP/LAM ratio was significant higher in KAP group, compared to non-M protein group. Reverse result was obtained in LAM group. There were higher Crea level and lower eGFR value in pure LAM light chain group, compared with IgG， IgA and IgM groups. Conclusion Immunofixation electrophoresis and KAP/LAM ratio may play an important role in the diagnosis of multiple myeloma patients with renal injury, so could be early screening markers.