An improved OFDM signal recognition algorithm is proposed to distinguish the zero-padding OFDM (ZPOFDM) signal from multicarrier signals. Based on the second-order cyclic cumulant of ZPOFDM and other signals and combined with a cyclostationary test, the algorithm can classify signals such as ZPOFDM, cyclic-prefix OFDM (CPOFDM), and single carrier signals in fading channel. The theoretical analysis and simulations confirm the effectiveness of discriminating multicarrier signals in frequency selective channels without synchronization and parameters estimation.