The effects of buoyancy on turbulence structure of a buoyant surface jet are investigated. Velocities and buoyancy fluctuations are simultaneously measured, and their statistic quantities are examined. Distributions of turbulence quantities are strongly affected by buoyancy. Their variations against the shear layer Richardson number can be explained in terms of the production terms in their transport equations. As the buoyancy effects increase, turbulence structure and buoyancy fluctuation balance change from a jet-like regime to a stratified flow-like one. This transition is well related with the large-scale coherent structure's dynamics peculiar to the turbulent shear flows. The buoyancy results in not only reduction of turbulence intensities but also diminution of turbulence scales.