Based on a 5.0 ps time resolved streak tube with length of 189.472 mm, the influence of grid gated impulse on the characters of the streak tube was discussed. It is found that the rising edge and falling edge of the gated impulse would deteriorate both temporal and spatial resolution capabilities of the streak tube. The spatial resolution may fall sharply to half when the voltage on grid has a fluctuation of 10%. The main cause for the destructive influence is that optimal imaging position shifts when the voltage on grid changes. Influence on temporal and spatial resolution would reinforce as the deviation of voltage on grid increases. In conclusion, the rising and falling edge of gated impulse on grid gated impulse should be controlled strictly in narrow to reduce the impairment on the streak tube.