For some scenarios where high received power cannot be guaranteed due to user moving, the OFDM system with low order M-QAM such as BPSK/QPSK is promising. This paper will propose an orthogonal parallel combinatory ASK modulated multicarrier system to achieve flexible bandwidth efficiency (BWE) using low order ASK modulation and parallel combinatory (PC) code. PC code has been shown that it can achieve flexible BWE and better peak-to-average power ratio (PAPR) performance. Our proposal will utilize PC code for both I-phase and Q-phase of frequency-domain OFDM symbol which further improve the BWE of PC-OFDM system. The proposed system can obtain better BER performance and better PAPR performance using low order ASK modulation. Therefore, the proposed system can simplify the receiver design and provide the design freedom degree with a flexible range of BWE for system design or adaptive modulation and code control.