In the last years, several proposals about Continuous Waveform (CW)have been developed, which in order to fit the automotive radar application requirements under the multi-target conditions. The transmit signal with Multiple Frequency Shift Keying (MFSK) technology was developed to analyze the target information in range domain and Doppler frequency domain simultaneously, but the MFSK waveform has lower estimation accuracy in phase measuring. A higher accuracy signal type is the chirp sequence waveform of monopulse radar, which is based on two dimensions independent frequency measuring. It can also get the range and velocity information, but might lead to ambiguities in Doppler domain. To avoid the Doppler ambiguity, a method is proposed in this paper, which using the modified chirp sequence waveform. The carrier frequencies of the modified chirp sequence are different, which causes the Doppler frequency offset. Doppler ambiguities have no influence on the Doppler frequency offset and the speed of targets can be derived from carrier frequency offset and Doppler frequency offset. Thus, the modified chirp sequence avoids the ambiguities in velocity and guarantees the measurement accuracy even in multi-target conditions. It has advantages in the automotive radar applications.