The present invention provides a modular building structure, comprising: a plurality of floor slab frames, a plurality of first wall panels, a plurality of second wall panels, a plurality of floor module boards, and a plurality of ceiling module boards. The two adjacent floor slab frames are connected through a plurality of clips, so as to fix the floor slab frames together. Through those structure, the workers can quickly build multiple floors with strength not much different from normal floors, while all the modular components ensure that they can be prefabricated in advance in the factory, which can also significantly improve the transportation efficiency.