Abstract: Balloon-borne electrochemical ozone-sonde is first used in detection of precise and fine ozone vertical distribution above Kunming area,located in the low latitude plateau of southwest China during the period of 28 February through 13 April,2001.The results show that ozone vertical profiles present the multi-layer pattern.The layer of the peak value of multimodes of ozone partial pressure is located in 21-30km.In this layer,averaged maximum is 15.13mPa.At 30.2km the ozone mixing ratio has the maximum.The minimum of ozone partial pressure near tropopause corresponds to the peak wind layer with south component.When the ozone peak value emerges in upper troposphere,there is significant cold advection close to the layer of peak value.An unstable high concentration peak layer of troposphere ozone is detected under 5km.