In current OFDMA systems, three major problems arise due to the large number of subcarriers, including high peak to average power ratio (PAPR), sensitivity to carrier frequency offset (CFO), and high complexity in user terminal. In this paper, based on an innovative concept of Layered FFT structure, we propose novel quadrature OFDMA system which can overcome these problems. In particular, the proposed system can achieve same guard-interval overhead and same bandwidth occupation to conventional OFDMA schemes, while with significantly reduced complexity and power consumption in user terminals. Simulation results show that the proposed quadrature OFDMA system can achieve similar and even better performance than conventional OFDMA systems, particularly when a minimum mean square error (MMSE) equalizer is applied.