Two-color quantum correlation between fundamental (1.56 mm) and second-harmonic (780 nm) fields is investigated by an external cavity- enhanced periodically poled lithium niobate frequency doubler. Centers wavelength of the system at 1560 nm and 780 nm are in the wave band of quantum states transmission and quantum storage, respectively. So this kind of system can be employed for researches of practical quantum information processing. When the second-harmonic power of 10 mW is obtained with the conversion efficiency of 45%, 1.2 dB quantum correlation between fundamental (1560 nm) and second-harmonic (780 nm) fields is observed.