A pulse-dilation framing tube with magnetic lenses was developed， the photocathode biased at -3 000 V was loaded with 10 V/ps oblique pulse. The pulse changed the accelerating voltage between the cathode and the anode， then the additional chromatic aberration which is proportional to the pulse slope was caused. The chromatic aberration characteristics of this tube were analyzed. The simulation results show that the spatial resolution on the axis decreases from about 60 lp/mm to about 2 lp/mm in 20 ps with ignore the time length of the electronic image； otherwise， the duration of the image is included， the spatial resolution on the axis decreases from about 20 lp/mm to about 2 lp/mm in 20 ps. The experimental setup is built according to the simulation， and the experimental results show that the modulation of the 2.5 lp/mm resolution mask declines 10% when the accelerating voltage decreases from -3 000 V to -2 860 V.