Precast structures are popular in recent years due to the merits of effectiveness, safety, high quality and environmental friendliness, etc. However, their behavior is different from that of cast-in-situ. This article investigates and compares two buildings with one precast and one constructed in-situ. The precast building built with a type of new precast superimposed slab shear wall system imported from Germany and it has been applied to different structures. However, this kind of structure may have the weakness of low integrate performance, lack of design and technical experience, more complex connections between components, and large transport costs. To know more about the dynamic characteristics and integrity of the precast system, two ambient vibration tests were conducted on two buildings. Modal identification was performed using vibration data to obtain their dynamic parameters. According to the identified results, the characteristics of different buildings are discussed and compared. Due to the different floor numbers of the two buildings, the final dynamic characteristics should not be totally the same, however, the identified mode shapes are consistent with each other.