Flow-induced vibration (FIV) of four separately mounted cantilever cylinders are experimentally investigated in a water flume.The four cylinders with top ends screwed vertically into a turntable platform are subjected to uniform flows with Reynolds number ranging from 3840 to 16520.A non-intrusive measurement with high-speed cameras is employed to simultaneously capture the time-varying in-line and cross-flow vibrations in the reduced velocity range of 3.0-12.9.Experimental results highlight the continuous adjustment of flow regime caused by the spatial-temporal alteration of cylinders.Consequently,the space-time varying flow interference contributes to the occurrence of multiple response frequencies.The transition from a dominant frequency to a broad-band response illustrates the enhancement of wake interference.The combination of wake flow interactions results in the irregular oscillation trajectories and the appearance of a response trough with the associated switching in vortex shedding mode.The dual-resonance phenomenon is observed in the four cylinders due to the complicated wake-structure interaction.The greatest mechanical energy possessed by the four cylinders in an in-line square arrangement is mainly resulted from the downstream cylinders,signifying the positive role of wake excitation in extracting hydrokinetic energy from ambient flow.