A security lock, having a lock tongue, a key cylinder (20), and a key (30). The key cylinder (20) has a main body (21), a cover (22), and a connection assembly (40). The main body (21) has a channel (24). An electronic control assembly (50) and a mechanical control assembly (60) controlling the connection assembly (40) are provided within the main body (21). The key (30) has an elongate portion (31) and a grip portion (32). A power supply and a control chip are provided within the grip portion (32). The elongate portion (31) has bitting cuts (33) and a first contact member (34) connecting to the control chip. During an unlock operation, the key (30) is inserted into the channel (24), the first contact member (34) is communicatively connected to the electronic control assembly (50), and the bitting cuts (33) press against the mechanical control assembly (60).