Using the method of OES (optical emission spectrum) for measuring N₂ emission spectrum,the spacial distribution of energetic electrons in multi-needle bipolar corona discharge at atmospheric pressure was investigated.According to the distribution of N₂ second positive band’s intensity I_SPB,the outline of ionisation region was drawn accurately.The relationship between I_SPB and discharge current I was obtained through the sum of I_SPB .There are two ionisation regions in the multi-needle bipolar corona discharge.One is near the HV electrode and the other is near the grounded electrode.The ionisation region exists around the needlepoint withiN₂-3 mm.The volume of ionisation region becomes big with the applied voltage U increasing.The ionisation region of negative corona is bigger than that of positive corona.Near the HV discharge electrode,the outline of electron avalanche is similar to the configuration of electric field lines in the ionisation region,so the electron avalanche along the axis direction of needle develops farther than that along the radial direction.The electric field in the migration area is weak,and the distribution of space charges is large along the radial direction.The sum of I_SPB in each ionisation region is second order linear with I,but the quadratic coefficient is very small.So the sum of I_SPB is nearly linear with I,the distribution of I_SPB is corresponding to the density distribution of energetic electrons.So the charged particles forming the discharge current in ionisation region are electrons.No emission spectrum of N₂ can be measured in migration area,so there is no energetic electron.The energetic electrons only exist in ionisation region and the charged particles in migration area are ions.