Bit line pre-charge circuit of static random access memory

The invention discloses a bit line pre-charge circuit of a static random access memory. The bit line pre-charge circuit comprises a bit line balancing circuit, a voltage judging circuit and a switch circuit, wherein the bit line balancing circuit is used for balancing voltages of a first bit line and a second bit line which are complementary and enabling the balanced voltages of the bit lines to become balanced voltages respectively; the voltage judging circuit is used for comparing the balanced voltages with a pre-charge threshold voltage and forming a pre-charge judgement signal according to a comparison result signal and a pre-charge enabling signal; the switch circuit is connected between a pre-charge voltage source and the first and second bit lines. During a pre-charge cycle, when the balanced voltages are greater than or equal to the pre-charge threshold voltage, both the voltages of the first bit line and the second bit line are kept as the balanced voltages; when the balanced voltages are smaller tha