A faucet installation tool includes at least two coupling units. Every adjacent two of the coupling units are detachably connected together. A hollow area is formed between middle portions of the coupling units. Tops of the coupling units are formed with a first socket portion. The first socket portion is configured to receive a lock nut used for installing and fixing a threaded connecting pipe of a faucet, improving the connection strength between the first socket portion and the lock nut. The faucet installation tool does not require a large lateral space and is convenient to tighten the lock nut when in use.