The invention relates to a cold-rolled galvanized duplex steel, wherein the substrate thereof comprises the following components by weight percentage: 0.08 to 0.18 wt.% of C, 0.50 to 1.50 wt.% of Si, 1.50 to 2.5 wt.% of Mn, 0.10 to 1.0 wt.% of Cr, 0.02 to 0.5 wt.% of Mo, 0.005 to 0.05 wt.% of Nb, 0.005 to 0.05 wt.% of Ti, 0.002 to 0.05 wt.% of T.Al, less than or equal to 0.02 wt.% of P, less thanor equal to 0.01 wt.% of S and less than or equal to 0.006 wt.% of N, and the balance of Fe. The manufacturing method thereof comprises the steps of: smelting in an oxygen top-blown convertor, refining in a heating steel ladle, continuously casting into a slab, and then conventionally hot rolling, pickling tandem rolling, galvanizing and annealing, wherein the critical annealing temperature is between 760 and 840 DEG C; the annealing is finished in the two-phase area of ferrite and austenite; 1CR section cooling has a cooling speed of 1 to 40 DEG C/S from the annealing temperature to the zincpool, putting the substrate into the zinc pool having a temperature of 450 to 465 DEG C so as to galvanize; and 2a CR section cooling has a cooling speed more than 3 DEG C/S. The steel of the invention has the advantages of high tensile strength, low yield ratio, capable of being press formed, excellent matching between strength and toughness, high rate of initially work-hardening and being free from yield extending.