An improved wavelet-based pulse design for ultrawideband (UWB) system is presented. Under the constraint of the peak frequency fmax which lies in bandwidth between 3.1 and 10.6 GHz, the algorithm changes the searching method from two dimensional random variables (a, f0) to one dimensional random variable (fmax). Through the search of the peak frequency, the algorithm adjusts factors of Morlet wavelet to meet the Federal Communications Commission (FCC) spectral mask for UWB system. Simulation results show that this algorithm can lead to the same results to primary algorithm.