Abstract: The characteristic of striation in DC glow discharge in non-uniform-radium tube in air has been investigated in experiments. To study the factors that affect the characteristic of striation, a stepped-tube was designed, and the relationships between the striation separation and the discharge current, the tube dimensions as well as the gas pressure were discussed. The results showed that the striation separation relates to the tube dimension as a function of faction index and decreases linearly with the pressure. The current density has also some effect on the striations.