Disclosed a no-added formaldehyde composite wood product binder, a no-added formaldehyde composite wood product manufactured by same, and a preparation method for the composite wood product. The no-added formaldehyde composite wood product binder comprises an agent A and an agent B. The agent A is an isocyanate-based binder, and the agent B is an aqueous dispersion of polyester based aliphatic polyurethane and/or a modified polyester-based aliphatic polyurethane. The no-added formaldehyde composite wood product is formed under hot-pressing after a wooden and/or straw material is mixed with the no-added formaldehyde composite wood product binder. The composite wood product manufactured by the no-added formaldehyde composite wood product binder has excellent water-proof and mechanical properties and a good saw cutting performance, and the amount of isocyanate used is also reduced, thereby reducing costs.