Abstract: [Objectives] To investigate the near-wall rotating cylindrical wake and hydrodynamic characteristics, flow past a rotating cylinder at typical gap ratios is investigated. [Methods] A numerical simulation of flow past a near-wall rotating cylinder with different gap ratios ( ) and rotation rates at Re=200 was carried out to compare the cylindrical wake and hydrodynamic characteristics at different gap ratios and rotation rates. [Results] The results show that: the cylindrical vortex shedding is significantly suppressed and the lift and drag force on the cylindrical surface remain steady. For . For and , at low rotation rates, the "wake vortex" is shed and is similar to the 2S pattern, with sinusoidal periodic fluctuations in the lift and drag coefficients and small amplitude; at higher positive rotation rates, the cylindrical wake pattern is the stable D pattern with no vortex shedding (changing from D+ to D- pattern as the rotation rate increases), the "wake vortex layer" is separated from the "wall vortex layer", the "wall vortex" is shed multi-periodically, the lift and drag coefficients are fluctuating multi-periodically and the amplitude is increasing significantly; at higher reverse rotation rates, the cylindrical surface is wrapped by a positive boundary layer, with no vortex shedding and no fluctuations in lift and drag. [Conclusions] The results described the wake and forces on a near-wall rotating cylinder at different gap ratios and rotation rates, which provided a reference for the study of effective flow control technique.