The invention discloses a long-chain-branch high-melt-strength polypropylene resin. The long-chain-branch high-melt-strength polypropylene resin is mainly prepared from, by mass, 100 parts of ethylene propylene co-polypropylene, 0.10-2 parts of an antioxidant, 0.05-1 part of a lubricant, 0.05-1 part of an antistatic agent, 0.01-3 parts of a peroxide initiator, 0.01-5 parts of a first grafted monomer and 0.01-5 parts of a second grafted monomer. The first grafted monomer is vinyl end-capped silicone oil, and the second grafted monomer is cycloolefin, styrene or their combination. The invention further discloses a preparation method of the polypropylene resin. The polypropylene resin is high in melt strength and is especially suitable for foaming, blistering, compression molding, film blowing and other applications.