A reusable Safe Link® can lock and unlock a bicycle chain tool free. Riders can enjoy great convenience and user friendliness in chain maintenance and chain replacement. The Safe Link® can lock and unlock only at 90-degree angle toward chain itself, turn the Safe Link® 90 degree back to the right the chain will safely lock. Besides, the stop pump design at the middle of the Safe Link® with lock function will ensure the safe connection of the chain, absolutely secure riding and shifting. The Safe Link® shape is similar to outer plates of chain to guarantee the shifting performance and the conformity appearance of the chain.