Abstract: By getting insight into the main affecting factors on the property of streak image tube and keeping the designing orientation on the improvement of such three performance parameters as temporal resolution, spatial resolution and dynamic range, an optimized scheme is achieved with introduction of an auxiliary accelerating electrode in the neighborhood of fluorescent screen. It is an equal-diameter spiral dielectric electrode, which can bring about a uniform axial accelerating field. Correspording discussion indicates that the electrode can optimize the performance of streak image tube in the following aspects: increasing the screen-intersected velocity of electrons and hence the screen brightness, decreasing the transition time span and relevant dispersion between the deflection plates and