Results show that the frequency spectrum characteristics of arc diffluence is accordance to jet fluctuation. Arc diffluence in the new gun is confined obviously.

Increase the compression degree can make arc of high temperature plasma jet extended, form more uniform high temperature area, and increase the speed of the jet, can reduce the width of the poor.

Special testing apparatus was built to study the effect of arc divided flow on the jet fluctuation and the inhibiting effect of new spray gun on the jet fluctuation.