A large eddy simulation algorithm for numerically calculating unsteady wind field around complex geometry building was given. In this algorithm, a curvilinear coordinate system was used to formulate the numerical model, so the complex wind-structure interface could be described precisely. Governing equations were discretized by central differencing schemes with co-located grids. The convection velocity was interpolated by using Rhie-Chow method in order to avoid the inherent odd-even decoupling problem. A common Maker and Cell (MAC) scheme was used to split the velocity-pressure linkage in Navier-Stockes (NS) equation. An explicit Adams-Bashforth differencing scheme was applied for time marching. A corresponding computer code was developed and was validated by performing on simulation of wind field around full-scale Texas Tech University (TTU) building model. Furthermore, the simulation results were compared with corresponding field measure data and wind-tunnel experiment results reported by other authors. The comparison showed that this algorithm is feasible for numerical simulation of unsteady wind field around buildings.