Abstract: The mechanical properties of deposited metals of five high strength marine steel electrods with different Mo contents were tested, the microstructures were observed and analyzed by optical microscope and transmission electron microscope, and the welding CCT diagrams of deposited metals were also analog computed by Jamtpro software. The results showed that with the increasing of Mo content, the yield strength and tensile strength of deposited metal significantly enhanced, while the ductility and toughness decreased evidently; welding CCT curves moved down to the right gradually, the microstructure of the deposited metal turned from acicular ferrite of good toughness to the brittle bainite and martensite; the M-A phase which would deteriorate deposited metal's toughness appeared when Mo content exceeded 0. 482%, and the Mo carbide would precipitate when Mo content exceeded 0. 887%, leading to severe embrittlement of deposited metal.