There are provided a semiconductor memory device and a method of precharging global input/output (I/O) lines thereof, for reducing power consumption during a precharge operation. The semiconductor memory device includes a pair of first global I/O lines; a pair of second global I/O lines; a first precharge circuit for precharging the pair of first global I/O lines in response to a first precharge enable signal; a second precharge circuit for precharging the pair of second global I/O lines in response to a second precharge enable signal; a switch for connecting the pair of first global I/O lines and the pair of second global I/O lines; a first precharge driver for enabling the first precharge enable signal during a precharge operation; and a second precharge driver for enabling the second precharge enable signal during a precharge operation.