Disclosed is a power failure detection circuit, including a first PMOS FET (mp1), a second PMOS FET (mp2), a first NMOS FET (mn2), a second NMOS FET (mn3) and a reset transistor (mn1). The PN junction area of the drain electrode of the first PMOS FET (mp1) is greater than the PN junction area of the drain electrode of the first NMOS FET (mn2). The PN junction area of the drain electrode of the second NMOS FET (mn3) is greater than the PN junction area of the drain electrode of the second PMOS FET (mp2). The power failure detection circuit of the present invention is novel in design and high in practicability.