Because of the change of using function of one masonry structure, its longitudinal walls need to be underpinned. The related members also need to be reinforced. This paper has a discussion on the thought of underpinning part, strengthening method and key construction process. They main involve the reinforcement of foundation, the transformation from non-bearing members to bearing members of ring beams and constructional columns. It also involves the construction points for attention during underpinning process. At last, the main points that shuold be paid attention to in strengthening deign and underpinning construction are concluded.