To study the affection of cast in-situ slabs in RC frames during earthquakes,this paper presents a low cyclic loading test for two spatial RC frames. The failure pattern, loading carrying capacity, stiffness degradation, deformation characteristic and energy dissipation capacity are experimentally studied. Research findings indicate that the loading carrying capacity of the frame with cast in-situ slabs increase and the deformation capacity decrease. However, the energy dissipation capacity changes slightly. The failure patterns of the frame with cast in-situ slabs changes from “strong column weak beam failure” to the “strong beam weak column”. The degradation of loading carrying capacity decreases and the stiffness degradation increases due to the effect of slabs. All the frames exhibit good seismic performance.