Abstract: This paper carries out a literature review on the in-plane mechanical behavior of complex structure floor slabs. Discussed are the basic in-plane mechanical behavior and mechanism of the slab, in-plane mechanical model of the slab, the influence of the in-plane mechanical behavior of the slab on the global structural behavior, and the design methods considering the in-plane behavior of the slab. Based on the relevant research, the problems that need to be resolved are put forwarded. The results of the literature review overall show that: the research results of concrete structures are relatively rich, while the research results of composite structures are relatively scarce, while composite structures are more competitive when applied to complex structures. Therefore, regarding composite structures in the future, an elaborate and efficient slab model for the in-plane nonlinear behavior considering out-of-plane composite effect will be further put forwarded, the influence of different in-plane mechanical slab model for the seismic behavior of the structural systems will be studied, a quantitative evaluating method for the error of in-plane simplified slab model will be developed, and a seismic design method for the composite structures considering their in-plane nonlinear behaviors of floor slabs will be put forwarded.