Wells turbines are used in oscillating water column wave energy system and the turbine has a stagger angle of 90o. Numerical analysis is performed to analyze the performance of the turbine in the present work. A commercial code ANSYSCFX ® v14.0 was used for the simulations at different flow coefficient, different angles and a constant rotational speed. The turbulence model was k-ω SST. Higher guide vane angle produced higher efficiency of the turbine and the efficiency (enhanced) change was contributed because of the vortex formation in different locations in the flow passage or near the blade surface. Copyright © 2014 by ASME.