Wake interaction normally occurs in all wind farms and impacts significantly the flow field and performance of downstream wind turbines. The present work aims to study the wind turbine wake interaction phenomenon through the CFD method using LES and actuator line model. The solver used in the present work is developed based on the open source C++ class library OpenFOAM, in which the PISO algorithm is applied to deal with the velocity pressure coupling problem. The simulations which consider uniform inflow condition and six different layouts are implemented to study the evolving process of the interacting wakes. From the numerical result, the interacting region of wakes contains higher level turbulent flow than the single wake. The fully developed turbulence appears the earliest in the case of tandem layout, leading to serious wake meandering in the end of computational domain. The diffusion of turbulence causes the merging of wakes, and thus the velocity is redistributed among the whole wake region. Velocity deficit caused by the wake decreases the convertible wind energy. The turbulent flow and meandering of the wake result in the multi-scale fluctuation of the aero-power curves of wind turbines downstream.