The present invention relates to a false lock prevention circuit and method which is used to cause a delayed locked loop (DLL) to escape from false lock such as harmonic lock or stuck lock, when the false lock occurred in the DLL, and a DLL using the same. The false lock prevention circuit includes a harmonic lock detector configured to detect harmonic lock and a stuck lock detector configured to detect stuck lock. The harmonic lock detector includes a plurality of flip-flops configured to sample a plurality of delayed clocks and a logic unit. The harmonic lock detector compares a reference clock signal with the plurality of delayed clock signals, and detects whether or not the positive edges deviate from one cycle of the reference clock signal.