A scheme of Fourier analysis for tropically climatological wind field (V) is put forward.850hPa tropically climatological wind field (V) is investigated from 30°S to 30°N in January,the results show that is characterized by low dimension and low order;the first nine wave components (|m|=0,4) fit 92.4% of modular square.The most important wave component V₀ (m=0),which fits 56.4% modular square of,characterizes the configuration of mean zonal trade winds.The stationary wave (V^*),fitting 43.6% modular square of,is also low-dimensional and low-order;the first eight wave components (|m|=1,4) of which the stationary wave wind field (V₄^*) consists,fit 82.6% of V^* modular square.The similar coefficient between V₄^* and the original stationary wave field (V^*) is 0.909,so that the V₄^* describes the major circulation systems of V^*.Therefore,Fourier analysis is very effective method to investigate the tropically climatological wind field.