Abstract: Based on actuator line method, numerical simulations were conducted on the wind farm with three 5 MW wind turbines in five different aligned arrangements using OpenFOAM. By comparing the total power output, the velocity fields and velocity profiles at the hub height of wind turbines for different wind farm layouts, the effects of upstream turbine wake on the downstream wind turbine were investigated. Results show that in an aligned arrangement, the power output may be reduced by 82.72% for the wind turbine lying in the wake. Changing the relative position of wind turbines reasonably could help to optimize the wind farm layout, when the total power output may be increased by a maximum of 11.8%, even if the output of an individual wind turbine declines somewhat.