Abstract: To investigate the power enhancement of large vertical axis wind turbines (VAWT) under different parallel arrangement spacings, and clarify the characteristics and differences of their wake flow fields across various dimensions, a large three-bladed H-type VAWT was selected as the research subject. The influence of paralleled spacing on the aerodynamic performance and flow field characteristics of VAWT units was analyzed through computational fluid dynamics methods in different dimensions. Results show that under the same arrangement spacing, both two-dimensional (2D) and three-dimensional (3D) parallel arrangements of VAWT exhibit an increase in output power, with the maximum enhancement observed at a spacing of 1.50 times of the rotor diameter. However, the power improvement obtained from two-dimensional simulations is significantly greater than that from three-dimensional simulations. The internal flow field characteristics of the VAWT rotor in three-dimensional simulations are more complex than those in two-dimensional simulations, with slight fluctuations in blade peak values during a single cycle. Furthermore, when the paralleled arrangement spacing is too small, the phenomenon of fluid acceleration channels between the units will be weakened, and the power increase will decrease. The three-dimensional visualization of the vortex tubes shows that the vortices in the wake are more difficult to dissipate, and the wake recovery requires a longer distance.