By using the June-September bandpass filtered grid data of 1984 from the ECMWF,the global distribution of 40-50 day oscillation of the 200 hPa wind field in summer and its fluctuation features are examined. Analysis indicates that the 40-50 day oscillation of the wind field has significant meridional-zonal phase propagation. It is found that the oscillation has a larger zonal scale and a greater phase propagation velocity in the tropics than in the extratropics; the zonal wind oscillation has a larger zonal scale but a smaller meridional scale than the meridional wind oscillation with their zonal propagation quicker than their meridional propagation; the zonal wind oscillation has a meridionally-arranged wavetrain structure while the meridional wind oscillation has a zonally-arranged wavetrain structure.