In the present paper we wish to propose a calculating method of power spectra and cross spectra of wind fluctuations averaged over a distance along a horizontal straight line in an arbitrary direction to mean wind direction and to show some results calculated according to the method. Examples of weighting functions related to space average, by which the original power spectra are cut off, are shown. When wind fluctuations are averaged over a distance, coherences between them at two different points usually become larger than the original ones. On the other hand, phase differences become smaller. A method for combining the effects of space average into a program for simulation of multi-dimensional wind fluctuations is proposed. The method simplifies the procedure of simulation of multi-dimensional space-averaged wind fluctuations, and is very convenient for practical use.