The invention discloses a modified polyurethane adhesive, a composite waterproof adhesive strip comprising the modified polyurethane adhesive, a preparation method and an application thereof; the modified polyurethane adhesive is prepared from the following components in parts by weight: 80-120 parts of TPU particles, 8-30 parts of PES particles, 0.5-3 parts of polycarbodiimide, 0.5-5 parts of closed crosslinking agent, 0.5-5 parts of coupling agent and 0.1-1 part of antioxidant. The modified polyurethane adhesive is extruded by a casting machine and thermally compounded on one side of the TPUfilm to obtain the composite waterproof adhesive strip, and the composite waterproof adhesive strip is soft, good in elasticity, good in water washing resistance, dry cleaning performance and water pressure resistance, large in bonding strength to coatings such as TPE, hydrophilic PU, TPFE and the like of windproof and waterproof clothes; the composite waterproof adhesive strip is not capable offalling off at the edges, so that the composite waterproof adhesive strip can be applied to outdoor sports clothes, particularly windproof and waterproof clothes, and has a good application prospect.