Abstract: After analyzing the actually wind and temperature data of hilly boundarylayerin Zhejiang Province,we find that the boundary-layer-jet over that area occurs frequently and has distinct features under high pressure situation.The analysis illustrates that,the layer-barocline-feature,resulting from the thermodynamic difference over hill terrain, derives from the inertial oscillation of turbulent intensity's daily variation,and the moment's do wnward transportation led by turbulence exchange are the essential mechanism of boundary-layer-jet's formation;while,the occurrence and development of hanging-inversion peculiarly in hilly area is the key factor to jet's lasting.