Extending the dynamic range of analog-to-digital converters (ADCs) is an important issue in their application field. This paper presents a novel nonlinear equalizer based on the cube coefficient subspace (CCS) architecture to mitigate nonlinearities inherent in ADCs. The proposed equalizer is verified with a 14-bit, 200-MSPS ADC injected a two-tone signal. Simulation results show that it achieves a 16.55 dB improvement in dynamic range with a computational complexity of 110 operations per sample (OPS). The improvement using the proposed equalizer is 14.12 dB and 2.67 dB greater than those using two conventional equalizers: the memory polynomial (MP) and horizontal coordinate system (HCS) equalizers, respectively, with the same computational complexity.