According to the application requirement of ICF system, an analysis model of energy superposing on the target plane of four-ultrashort chirped Gaussian pulses was established. By using the analytical expression of the envelope of complex exponential function, the spatial singularity of one pulse and superposition of multi-pulses were analyzed by numerical simulation. The results show that the pulse width is the main factor to influence the spatial singularity phenomenon of the ultrashort chirped Gaussian pulse. While the pulse width was less than one oscillation period, the parameters should be controlled carefully within reasonable horizontal distance, which was less than 1w0 in order to prevent the spatial singularity.