This work establishes a three-dimensional CFD model that is capable of describing the counter-current air-water flow across a staggered tube bundle in a bench-scale wet cooling tower (CWCT) by combining the VOF multiphase method and the SST k-ω turbulence model. One important feature of the proposed model is that it investigates the interaction mechanisms among multiple tubes in the staggered tube bundle, which can reduce the gap between simulation and experiment. Through adding the air-water shear force term and water evaporation equation in the model, the effects of the spray density and the inlet air velocity on the falling film flow mode, air temperature in CWCT were studied. The numerical results show that, the inlet air velocity can largely influence the flow mode in CWCT. Under the spray density of 0.048 kg∙m-1∙s-1 and 0.060 kg∙m-1∙s-1 in which condition the Rew is greater than 288, the falling film flow develops into column mode. The air temperature changes logarithmically along height direction, and their increase rates enlarge with the increment of spray water, but decrease with the increase of ua,in. These results provide an insight into the complex mechanisms of heat-mass transfer for CWCTs.