In the area of the speech synthesis techniques, the waveform coding methods maintain the intelligibility and naturalness of synthetic speech. In order to apply the waveform coding techniques to synthesis by rule, we must be able to alter the pitch of synthetic speech. In this paper, we propose a new pitch alteration method that compensates the formant and phase information by using the inverse filter of LP analysis and the pitch alteration method of the time domain. For performance test we used as the spectrum distortion rate as objective criterion and the MOS(Mean Opinion Score) was used as subjective criterion. As a result, the spectrum distortion and MOS are obtained by 0.6% and 4.0, respectively.