Abstract: A sub-threshold monostable PUF circuit with an SRAM function and an entropy source extraction function includes a mode configuration circuit, a decoding circuit, a PUF array and a reading circuit. The PUF array has a SRAM storage mode and a PUF mode for generating an entropy source voltage. The PUF array includes m*n PUF cells and n pre-charge modules. Each PUF cell includes a first PMOS transistor, a second PMOS transistor, a third PMOS transistor, a first NMOS transistor, a second NMOS transistor, a third NMOS transistor, a fourth NMOS transistor, a fifth NMOS transistor and a sixth NMOS transistor. The monostable PUF array formed by PUF cells is constructed only by adding a first PMOS transistor, a first NMOS transistor and a fourth NMOS transistor in each SRAM cell of an original SRAM storage array of IoT equipment.