The invention discloses a subthreshold SRAM (Static Random Access memory) unit circuit capable of increasing read noise tolerance and writing margin, first PMOS transistor MP1, first NMOS transistor MN1, third NMOS transistor MN3 and third PMOS transistor MP3 form a first inverter, second PMOS transistor MP2, second NMOS transistor MN2, fourth NMOS transistor MN4 and fourth PMOS transistor MP4 form a second inverter, the first inverter and the second inverter are used for storing opposite data, namely data of memory point Q and memory point QB; seventh NMOS transistor MN7 and eighth NMOS transistor MN8 are used for controlling read operation, the third NMOS transistor MN3, the third PMOS transistor MP3, the fourth NMOS transistor MN4 and the fourth PMOS transistor MP4 are used for improving writing capability. The SRAM (Static Random Access memory) unit circuit improves the ability of writing data, a new writing operation method is used, so that the data is easy to write in a unit, the write margin is greatly improved; meanwhile, the unit circuit adopts a read-write separation structure, so that the read noise tolerance reaches to the maximum, and the unit circuit can works in a subthreshold zone, and reduces power consumption.