Fiber reinforced polymer (FRP) composites are becoming more frequently used in civil engineering structures because of their superiors advantages. While in practice, partial deterioration of concrete columns occurs occasionally, frost damage, aging or construction quality might lead to concrete deterioration. However, confined the whole columns including intact and deteriorated parts has been regarded as a waste. Few literatures have involved in partial confinement only to defect parts. The objective of this paper is to present an effective method to deal with the partial deteriorated strength columns, and to gain insight into the mechanical behavior of the defect part. Five groups of plain square columns are cast, different layers of CFRP sheets have been wrapped just on the deteriorated part to investigate the improvement with CFRP sheets and to verify the practicability of partial confinement. Columns are subjected to monotonic axial compression until failure occurs. Axial load, axial and transverse strains are measured to compare the different behaviors and to evaluate confinement level supplied by CFRP sheets. Experimental results show that partial confinement with CFRP can significantly enhance the strength and the ductility of the deteriorated strength part, then, the load capacity of the entire column can be improved subsequently.