Packet detection always has been critical in the design of an OFDM receiver because failure of signal detections causes packet loss which degrades performance of receiver. In multi-band OFDM(MB-OFDM) system, first task of receiver is to perform signal detection which detects an incoming packet and acquires the TFC (time frequency code) of the packet. Auto-correlation based algorithms for signal detection are not suitable for MB-OFDM systems due to high hardware complexity. Cross-correlation requires less hardware but it is weak to frequency offset which severely degrades detection performance. A novel cross-correlation based scheme is proposed to reduce the synchronization failure probability by adopting verification mode. The proposed algorithm shows a very low synchronization failure probability around 10-4 and it is very useful for MB-OFDM synchronization which requires robust synchronization.