Disclosed are a corrosion-resistant marine composite steel plate and a manufacturing method therefor. The corrosion-resistant composite steel plate has a two-layer structure, wherein one layer is duplex stainless steel, and the other layer is marine carbon steel; said duplex stainless steel comprises the following components by weight: C≤0.03%, Mn≤2.00%, Si≤1.00%, Cr: 21.0-23.0%, Ni: 4.5-6.5%, Mo: 2.5-3.5%, N: 0.08-0.20%, P≤0.02%, S≤0.025%, and the balance being Fe and inevitable impurities; and said marine carbon steel comprises the following components by weight: 0.03%≤C≤0.13%, Si≤0.50%, Mn: 0.90-1.60%, P≤0.020%, S≤0.025%, Cu≤0.035%, Cr≤0.20%, Ni≤0.40%, Nb: 0.02-0.05%, Ti≤0.02%, Mo≤0.08%, Al≥0.015%, and the balance being Fe and inevitable impurities. A rolled composite steel plate is produced by using a double-barrier vacuum assembly method, so that a reduction in structure weight is achieved while a good structural strength and an excellent corrosion resistance are obtained