Abstract: In hypersonic target searching application, the transmitted radar signal was required to have characteristics of high resolution, low probability of intercept (LPI) and high Doppler tolerance. In order to overcome the disadvantage of OFDM signal’s low Doppler tolerance, a new type of multi-carrier radar signal with non-uniform frequency density was proposed and the design method of subcarriers frequency based on NLFM signal’s spectrum window function was given. Under the condition of equal subcarrier bandwidth, its subcarriers’ spectrum had larger density at frequencies that need to be enhanced. At the same time, the distribution of the signal’s subcarriers with non-uniform frequency density had a significantly weighting effect on its overall spectrum. Theoretical analysis and numerical simulation were adopted to derive and compute the spectrum characteristics and ambiguity-function (AF) characteristics of the proposed signal, and the same characteristics of typical OFDM signal were compared. The results show that the new signal has advantages of higher Doppler tolerance, no range-Doppler coupling, faster out-of-band attenuation and lower side-lobe of time-delay autocorrelation function (ACF), which is suitable for wideband high resolution radar to search and detect high speed  target.