An assembly of a wrench and a socket. The wrench has a penetrating driving hole, which has a retaining ring mounted therein. The socket, having a front end and a tail end, comprises a socketing portion axially extended between the front end and the tail end thereof for driving a fastening element. The socket comprises a retaining portion formed on the periphery thereof. The retaining portion has a retaining groove arranged at retaining corners radially indented for matching the retaining ring. The retaining groove is positioned between the front end and the tail end. The retaining portion further has a buffer groove formed between the retaining groove and the front end, so as to allow the buffer groove to successively provide a buffer or damping effect with the retaining ring when the retaining groove is decoupled from the retaining ring. Accordingly, the user is allowed to control his/her force more easily and improves the operational safety for the process of pulling out of the socket.