The study explored the characteristics and correlation factors of transformation in subclasses of class IV lupus nephritis. Patients with class IV lupus nephritis were subjected to repeat biopsies after 6 months of induction treatment. Transformation rate between two subclasses, class IV-S and class IV-G, was compared. Influence Factors of transformation were evaluated. Class IV-G had more severe hypertension and higher score of immunofluorescence index, glomerular active lesions, tubular and vascular lesions. Class IV-S had a higher percentage of glomerular fibrinoid necrosis. Class IV-S appeared a higher rate of transformation to class II than class IV-G (57% vs. 27%). In each subclass, active lesion also showed a higher rate of transformation to class II than active/chronic lesion (IV-G: 41.2% vs. 12.5%; IV-S: 71.4% vs. 42.8%). Patients who maintained class IV had higher blood pressure, obvious proteinuria, declined kidney function, and lower C3 level. Immunosuppressive therapy, urine protein, and vascular lesions were independent risk factors for the pathologic transformation. The rate of transformation in class IV-S was higher than that in class IV-G. The transformation is most likely to benefit from immunosuppressive therapy. Urine protein and vascular lesions are correlated with the transformation in class IV lupus nephritis.