Abstract: This paper describes an experimental research on 3 damaged steel reinforced L shape section concretecolumns and a damaged normal L shape section concrete column strengthened by steel encasement under horizontallow cyclic loading. Based on the test results, failure mode, the hysteretic curves, energy dissipation, ductility andstiffness degradation were examined. The results indicated that, the failure mode of the column enhanced by steelencasement was concrete crush of the web of the columns, and their hysteretic curves were plump, and theyperformed good seismic performance.