This paper analyses some kinds of fissures in walls of a multi-story masonry buildings with additional floor transformation, and puts up several methods for dealing with the fissures. Through the spot inspection and computation analysis, the reason of crack producing is put forward. Because the ring beams only built in the first and the top floor, and precast floor slabs used in the building, the overall structure rigidity is poor. The internal longitudinal wall is strengthened by steel tension bar, simultaneously; an addition shallow submersion foundation is added on the original foundation. After the reinforcement processing, the structure is complete until now.