This paper analyses time-domain waveform and its unilateral energy spectral density based on the Gaussian pulse former 12 derivative functions. We could conclude that pulse forming factor has a closer relationship with different order number derived function affected the energy spectral density. Therefore, in order to maximize the approximate Federal Communications Commission (FCC) emission mask as much as possible, an iterative algorithm is proposed to optimize the linear combination of the Gaussian pulse former 12 order derived function. Compared with single differential Gaussian pulse, the simulation results show that after linear combination, new ultra-wideband pulse signal could greatly meet the spectrum utilization and indoor radiation mask standards promulgated by the FCC.