Abstract: Marine riser is a slender tube used to connect the oil platform and the subsea oil well. Under the excitation of waves and currents, risers often experience vortex-induced vibration (VIV). In deepwater oil production, several risers are often arranged into a riser array, which makes the VIV of marine risers more complicated. In this paper,cylinders of three types of cross-sectional shape, a cactus-shape, circular shape, and circular shape with strakes, are studied. VIV responses of an isolated cylinder and cylinder arrays consisting of four cylinders with a 2-by-2 arrangement were investigated. The results show that the cactus-shaped cross-section has a certain effect of suppressing VIV and can reduces the fatigue damage of the riser.