Helicon,known as a plasma source with high density,has shown its great potential in material modification,surface treatment and thruster[1.2].In this work,we studied the mode transition of discharge in N2 helicon and explored the mechanisms on different modes in radial region.The helicon plasma is produced in a quartz tube at 0.3 Pa with uniform magnetic field in the axial direction.The magnetic field is about 300 Gauss and the RF power ranges from 60 to 1400 W.An ICCD camera is used to record the discharge images and OES diagnostic is employed.