This letter proposes a transform domain communication system (TDCS) based on chirp noise sequence to deal with its high peak to average power ratio (PAPR). The optimal chirp noise sequence is obtained by the selective mapping to improve PAPR reduction of the proposed TDCS waveform with low complexity. Compared with other PAPR reduction algorithms, such as magnitude weighting selection and complementary peak reducing signal, the proposed TDCS based on optimal chirp noise sequence has about 1.5 dB PAPR reduction gain without extra bit error rate loss.