In order to further improve the precision of estimating the instantaneous frequency in radar signal processing, a new Morlet wavelet atom, based on the known Morlet wavelet atom to extract the signal wavelet ridge feature (WRF) is put forward. By analyzing the wavelet ridge principium and the qualifications of wavelet atom for extracting the WRF rightly in-depth, the WRF of radar emitter signals can be extracted. Consequently, the instantaneous frequency can be estimated. The new -Morlet has better performance of time-frequency colligation character in contrasts with the known Morler wavelet atom. At the same time, the iterative algorithm of estimating the instantaneous frequency is analyzed, which is based on the wavelet ridge principium. The computer simulation experiment results also show that the new-Morlet wavelet atom has better performances in detecting WRF and counteracting noise than the common Morlet wavelet atom. The experiment proves the effectiveness of the method.