Abstract:The working principle of pulse-dilation framing camera and Rayleigh criterion are introduced. The spatial resolution and modulation on-axis of pulse-dilation framing camera are calculated by using Rayleigh criterion through building model, simulating magnetic field, tracking electron trajectory and fitting histogram of imaging distribution. The research results show that, when the 10 000 electrons are emitted from adjacent object points on the photocathode, the imaging modulation of two fully distinguishable adjacent object points is 98.5732%, the spatial resolution is 194.523 7 μm; the modulation of just distinguishable is 19.16%, the spatial resolution is 73.22 μm; the modulation of undistinguishable is 0.14%, the spatial resolution is 4.7 μm. This work can provide a visualized solution for calculating spatial modulation transfer function of 2D ultrafast diagnosis device.