Method and device for detecting the process corner of a transistor are provided. The process corner detection method includes providing a ring oscillator. The ring oscillator includes an odd number of oscillation units connected in series and an output port of one of the oscillation units serves as the output port of the ring oscillator to output an oscillation signal. Each oscillation unit is constructed based on a PMOS transistor and an NMOS transistor. The process corner detection method further includes measuring the period of the oscillation signal and the maintaining time of the oscillation signal at a high level and a low level in each cycle; and determining the process corner of the PMOS transistor and the NMOS transistor in the oscillation unit based on the period of the oscillation signal and the maintaining time of the oscillation signal at a high level and a low level in each cycle.