The invention relates to a protein marker of focal segmental glomerulosclerosis, and more specifically relates to an application of a connecting part selectively connected to one or more proteins in preparing a diagnostic reagent in a development process of human focal segmental glomerulosclerosis. The one or more proteins are selected from [alpha]1 antiprotease, alpha albumin, serum albumin, beta-2-microglobulin, ceruloplasmin, fetuin-B, kininogen, serum transferrin, carboxylesterase, immune globulin gamma-2A chain C region, plasminogen, lysosomal acid phosphatase, protein YIPF3, zinc [alpha]2 glycoprotein, alpha-2-HS-glycoprotein, protein AMBP or T cell immune globulin. Specifically, the invention relates to the application of a urine protein potential marker of human focal segmental glomerulosclerosis obtained by a rat model and mass spectrometry.