Abstract: In Sept. 1988 and Aug. 1990,two observational experiments have been carried out in the HEIFE Gobi station. A data set on the surface layer turbulence has been collected, which is proved to be of high quality. An analysis on the surface layer structure shows that turbulence statistics such as the variances of vertical wind component and temperature are in good agreement with the surface layer similarity theory. The relevant forms of similarity function are presented.The characteristics of spectra and cospectra are mainly similar to that of flat and horizontal terrain. The phenomenon of downward water vapor flux over Gobi desert in daytime, which was noticed in 1988,was confirmed in the PIOP of 1990. An analysis on its physical mechanism is given. As the well-known ‘oasis effect',this phenomenon is closely related to a loca ‘Gobi desert-oasis' circulation system.